Usmle part 1
part 15
DANIL HAMMOUDI.MD
- Hydroureteronephrosis is the most significant renal functional alteration of pregnancy, accounted for by both hormonal and mechanical factors.
- Increases in circulating estrogenic, progestational and prostaglandin-like agents are known to cause ureterectasis in the absence of obstruction during pregnancy .
- Stasis caused by dextrorotation of the expanding uterus is the principal mechanical factor leading to hydroureteronephrosis of pregnancy and explains its tendency to occur on the right.
- Glomerular filtration rate (GFR) and renal plasma flow (RPF) are ordinarily increased during pregnancy .
- Both of these changes are attributable to increases in cardiac output, decreases in renal vascular resistance and increases in serum levels of progesterone, aldosterone, deoxycorticosterone, placental lactogen and chorionic gonadotropin .
- Increased urinary excretion of glucose, amino acids, protein and vitamins are consequent to increases in RPF and GFR .
- Renal volume is seen to increase during pregnancy up to 30% normal size, a result of increased RPF and glomerular surface area under the influence of prolactin and its growth hormone-type of effect .
- In addition, we see hypercalciuria as a concomitant of pregnancy due to increased GFR, calcium filtration and intestinal calcium absorption related to high levels of plasma calcitriol .
- However, an increase in inhibitors of stone-formation such as citrate, magnesium and glycosaminoglycans yields the result that pregnancy is unassociated with a net change in rates of stone formation
- .
- While increases in GFR of pregnancy would ordinarily cause the loss of 5,000 to 10,000 mEq sodium daily , there are mitigating factors resulting in maintenance of sodium homeostasis among which are tubular reabsorption , and increases in mineralocorticoid-like compounds such as aldosterone , deoxycorticosterone , estrogens , ACTH, prolactin, cortisol, growth hormone and placental lactogen .
- The influence of the renin-angiotensin axis upon sodium homeostasis is mediated by aldosterone metabolism and volume status .
- Physical factors affecting sodium regulation during pregnancy are increases in ureteral pressure and uterine blood supply.
- Thus, the net effect of the multiple aforementioned factors upon sodium metabolism is a slight sodium retention in pregnant subjects.
- During the latter portion of pregnancy the placenta secretes a growth like hormone = human lactogen placental =hPL , which antagonist the action of insulin secretion =èplasma insulin concentration during tolerance test is increased equivalent of the mid luteal phase of the menstrual cycle.
- Ovarian estrogen and progesterone are low due to the high level estrogen progesterone from the placenta that inhibit the pituitary secretion LH/FSH.
DIHYDROXYACETONE PHOSPHATE IS THE INTERMEDIATE PRODUCTS OF GLYCOLYSIS FOR FAT STORAGE.
Storage in the adipose tissue is catalysed by lipoprotein lipase, the activity of which is stimulated by insulin(the same hormone which stimulates storage of glucose as glycogen).
ß-oxidation of fatty acids
This is a cyclic series of reactions (occurring within the mitochondria) with the end result of two carbon units being hydrolysed from the fatty acid chain with each cycle. These two carbon units are molecules of acetyl CoA.
With each oxidation cycle, a molecule of NAD is reduced to NADH and one FAD is reduced to FADH. These are re-oxidised by the electron transport chainwith the energy released coupled to ATP synthesis.
The acetyl CoA molecules formed in each cycle are oxidised to CO2in the citric acid cycle, with the oxidation/reduction reactions coupled to the electron transport chain and further ATP synthesis.
These events occur in liver and muscle. During sustained exercise the cells of slow twitch muscle fibres (which possess mitochondria) utilise ß-oxidation as the major source of ATP.
Ketone bodies
An alternative method of utilising the acetyl CoA formed by ß-oxidation is via the synthesis and subsequent oxidation of four-carbon units known collectively as ketone bodies.
Acetyl CoA is converted in the liver into acetoacetate (essentially two acetyl groups covalently linked). Acetoacetate can be further reduced to form ß-hydroxybutyrate. These two compounds are referred to as ketone bodies. Their synthesis occurs in the liver.
They diffuse from the liver into the circulation and are used as fuels by several tissues. Heart muscle and renal cortex, in particular, use acetoacetate in preference to glucose. In contrast, glucose is the major fuel for the brain and erythrocytes in a human on a balanced diet. The brain has the capacity to adapt to the use of acetoacetate during starvation (and in the metabolic disease diabetes mellitus). In starvation of long standing, acetoacetate meets more than 70% of the energy needs of the brain.
This ability of the brain to adapt to the use of acetoacetate is important because fatty acids cannot enter neural tissue. Acetoacetate is regarded as a water soluble and readily transported form of acetyl CoA.
The efficiency (amount of ATP produced) of oxidation of fatty acids directly or via formation of ketone bodies is approximately the same - there is no penalty to the body in converting acetyl CoA to this water soluble form.
It is important to be aware thatthere is no mechanism in animals for the conversion of fatty acids to glucose.
Fatty acid synthesis
This occurs in the cytoplasm of cells (compared to ß-oxidation which occurs inside the mitochondria).
The process begins with acetyl CoA and cyclic reactions join two-carbon units to the growing fatty acid chain. The completion of the synthesis and the formation of unsaturated fatty acids is complex.
The role of fatty acid synthesis is to :
supply the body's needs for particular fatty acids not supplied in the diet AND
to convert excess dietary glucose to fatty acids for storage
Glucose is converted to pyruvate (glycolysis), then to acetyl CoA which, when ATP is required, is oxidised by the citric acid cycle. If the glucose intake exceeds the body's energy needs (and after saturation of glycogen stores) the acetyl CoA can be used for fatty acid synthesis (in the liver) and storage as triglyceride in adipose tissue.
A newborn presents with severe
acidosis, vomiting, hypotonia, and neurologic deficits. Serum analysis reveals
elevated levels of lactate and alanine. These observations suggest a deficiency
in which of the following enzymes?
A. Alanine aminotransferase
B. Glutamate dehydrogenase
C. Lactate dehydrogenase
D. Pyruvate carboxylase
E. Pyruvate dehydrogenase
A group of patients with lung
cancer is matched to a group of patients without lung cancer. Their smoking
habits over the course of their lives is compared.
Based on this information, researchers compute the rate of lung cancer in
patients who smoke versus those who never smoked. This is an example of
A. case-control
study
B. cohort study
C. cross-sectional study
D. longitudinal study
E. randomized control study
A pharmacologist is examining a
new drug with potential sedative properties. He begins by analyzing the
pharmacokinetic properties of the drug. Studies of the drug's rate of
elimination yield the above data. Which of the following drugs has similar
kinetics to the drug being studied?
A. Carbamazepine
B. Cimetidine
C. Ethanol
D.
Ketoconazole
E.
Phenobarbital
A 46-year-old woman presents to
her doctor complaining of weakness and fatigue. On physical examination, her
physician notices a 10-pound weight gain since her last visit 6 months ago. Her
blood pressure is 160/100 mmHg. Blood tests reveal serum Na+ 155 mEq/L, K+ 2.8
mEq/L, and a decreased serum renin. Which of the following is the most likely
diagnosis?
A. Cushing's
syndrome
B. Diabetes
mellitus
C.
Pheochromocytoma
D. Primary
aldosteronism
E. Secondary
aldosteronism
A 38-year-old woman complains
of cold, painful fingertips, as well as difficulty swallowing and indigestion.
Physical examination is remarkable for a thickened, shiny epidermis over the
entire body, with restriction of movement of the extremities, particularly the
fingers, which appear claw-like. Which of the following autoantibodies is likely
to be found in this patient's serum?
A. Anti-DNA topoisomerase I (anti-Scl-70)
B.
Anti-double-stranded DNA (ds DNA)
C. Anti-IgG
D. Anti-Sm
E.
Anti-SS-A
A 26-year-old woman and her
29-year-old husband have been trying to have a child for the last 3 years.
During this time the woman has had 5 spontaneous abortions. The karyotypes of
the mother, father, and the most recently aborted fetus all contained 46
chromosomes, and all pairs were normal except for the pairs shown below.
The
event that led to the child's abnormal karyotype was:
A.
adjacent I segregation
B.
adjacent II segregation
C.
alternate segregation
D. a
recombination event within a paracentric inversion
E. a recombination event within a pericentric
inversion
A 70-year-old woman undergoes a
gastrectomy for Zollinger-Ellison syndrome. Her doctor informs her that she will
need to take intramuscular vitamin B12 shots for the rest of her life. Absence
of which of the following cell types is responsible for
this vitamin replacement requirement?
A. Chief cells
B. G cells
C. Goblet cells
D. Mucous neck cells
E. Parietal cells
A patient presents with right
lower quadrant pain, fever, and diarrhea. Physical examination reveals diffuse
abdominal tenderness; laboratory examination reveals a moderate leukocytosis,
leading to a presumptive diagnosis of acute appendicitis. Surgical exploration
of the abdomen reveals mesenteric adenitis, but the appendix is normal. Which of
the following organisms is most likely responsible for these signs and
symptoms?
A. Clostridium
difficile
B.
Enterohemorrhagic E. coli
C. Enteroinvasive E. coli
D. Enteropathogenic E. coli
E. Yersinia enterocolitica
Mean
arterial blood pressure (MAP) and heart rate (HR) measurements were recorded
during the intravenous administration of two different drugs. Select the most
likely drugs given at the indicated points.
A. X, Acetylcholine Y,phentolamine
B. X, epinephrine Y,hexamethonium
C. X, isoproterenol Y, propranolol
D. X, metaproterenol Y,
propranolol
E. X, norepinephrine
Y, hexamethonium
A 21-year-old man is competing
in a weight-lifting competition. He lifts 325 lbs over his head and holds it
there for 5 seconds. Suddenly, his arms give way and he drops the weights to the
floor. Which of the following receptors is responsible for this sudden muscle
relaxation?
A. Free nerve
ending
B. Golgi tendon
organ
C. Merkel's disk
D. Muscle spindle
A normal volunteer consents to
an intravenous infusion of p-aminohippuric acid (PAH). After a short time, the
plasma PAH is 0.02 mg/ml, the concentration of PAH in urine is 13 mg/ml and the
urine flow is 1.0 ml/min. What is the effective renal plasma flow?
A. 0.26 ml/min
B. 26 ml/min
C. 65 ml/min
D. 260 ml/min
E. 650 ml/min
A 4-day-old male is brought to
the pediatric clinic because of breathing difficulties and poor feeding. He
coughs, chokes, and spits up milk very soon after beginning to suckle. Physical
exam and radiographs reveal the presence of the most common type of
tracheoesophageal fistula. The baby's defect likely resulted from:
A.
failure of the buccopharyngeal membrane to rupture
B. failure of the tracheoesophageal ridges to fuse
C. incomplete formation of the septum
secundum
D. incomplete
recanalization of the larynx
E.
patent thyroglossal duct
A 4-month-old blue-eyed,
fair-skinned child who appeared normal at birth is brought to the pediatrician
because of the development of scaly skin lesions and seizures. On physical
examination, the infant appears to be mentally retarded, and a musty odor is
noted. Which of the following defects is responsible for this child's
illness?
A. Deficiency of
alpha-ketoacid decarboxylase
B.
Deficiency of hexosaminidase A
C. Deficiency of homogentisate oxidase
D. Deficiency of hypoxanthine-guanine
phosphoribosyltransferase
E.
Deficiency of phenylalanine hydroxylase
A 31-year-old stockbroker
drives to a high-altitude mountain resort to do some rock-climbing. Later that
day, he experiences headache, fatigue, dizziness, and nausea. Which point on the
graph above best corresponds to the relationship between plasma bicarbonate, pH,
and PCO2 in this patient?
A.
Point A
B. Point B
C. Point C
D. Point D
E.
Point E
A 13-year-old male presents to
the emergency room with a deep skin abrasion on his knee. He states that it has
not stopped bleeding since it happened during recess approximately 20-30 minutes
ago. Physical examination reveals a well-developed, well-nourished adolescent.
There are multiple purpura over his legs and arms, and
a few scattered petechiae on his chest and gums. His bleeding time is 22
minutes, platelets = 300,000/mm3, hemoglobin = 11g/dL. A trial of
cryoprecipitate transfusion does not improve his bleeding time. A normal
platelet transfusion does improve bleeding time. Which of the following is the
correct diagnosis?
A.
Bernard-Soulier syndrome
B.
Henoch-Schönlein purpura
C.
Idiopathic thrombocytopenic purpura
D. Thrombotic thrombocytopenic purpura
E. Von Willebrand's disease
An 88-year-old male complaining
of abdominal pain enters the emergency room with his wife. A mini-mental status
exam reveals pronounced forgetfulness and confusion. The patient is discovered
to have acute appendicitis requiring immediate surgery. He is unable to
understand the situation and cannot provide informed consent. Which of the
following further actions must the physician take?
A. Do not perform surgery
B. Have another doctor confirm the necessity of
surgery
C. Obtain a court order
to perform surgery
D. Obtain
consent from his wife to perform surgery
E. Try to persuade the patient to consent to
surgery
A 42-year-old obese woman
experiences episodic abdominal pain. She notes that the pain increases after the
ingestion of a fatty meal. The action of which of the following hormones is
responsible for the postprandial intensification of her symptoms?
A. Cholecystokinin
B. Gastrin
C. Pepsin
D.
Secretin
E.
Somatostatin
Which of the pharyngeal pouches
develops into the palatine tonsil?
A. First
B.
Second
C. Third
D. Fourth
E. Fifth
A worried mother complains to
her pediatrician that both she and her 6-year-old son's teacher have noticed
that the child has become inattentive. She states that her son frequently stops
what he is doing and "stares blankly into space" before resuming his activities.
Electroencephalography reveals a 3/second spike and slow wave pattern of
discharges. Which of the following agents would most effectively treat this
child's disorder?
A.
Carbamazepine
B.
Diazepam
C.
Ethosuximide
D.
Methylphenidate
E.
Phenytoin
In the family shown above,
individuals affected with profound deafness are represented by a shaded symbol.
The phenotypes of individuals in the fourth generation can best be explained by:
A. autosomal dominant
inheritance
B. locus
heterogeneity
C. mitochondrial
inheritance
D. multifactorial
inheritance
E. X-linked dominant
inheritance
At which point on the diagram
above would the length of the myocardial sarcomere be approximately 2 mm with
maximal actin-myosin cross bridging?
A. A
B.
B
C. C
D. D
E. E
Absence of which of the
following enzymes would impair the rate-limiting step of
glycogenolysis?
A.
alpha-1,4-glucan transferase
B. Glycogen phosphorylase
C. Glycogen synthase
D. Phosphoglucomutase
E. UDP-glucose pyrophosphorylase
A 34-year-old female is brought
to her family physician by her brother. He states that the patient's husband had
run away with another woman the previous day. After discovering this, the
patient arrived at her brother's home in a "dazed state," was unable to function
appropriately the remainder of the evening, and slept fitfully all night. Early
in the morning she began to talk to people who were not present, and debated
whether or not to kill her children and herself. He denies anything like this
ever happening before. Which of the following is the most likely
diagnosis?
A. Bipolar
disorder
B. Brief psychotic
disorder
C. Schizoaffective
disorder
D. Schizophrenic
disorder
E. Schizophreniform
disorder
A 34-year-old woman presents
with abdominal pain and reports changes in her bowel habits. On pelvic
examination a mass is palpated on her right ovary. Laparoscopic surgery is
performed and the mass is removed. The gross appearance of the tumor is shown
below. What type of tumor is it?
A. Choriocarcinoma
B. Dysgerminoma
C. Fibroma
D.
Granulosa-theca cell
E.
Teratoma
A 55-year-old woman is
receiving chemotherapy for non-Hodgkin's lymphoma. Several days after a
treatment, she notes that she has blood in her urine. Which of the following
antineoplastic drugs is most likely responsible for this side
effect?
A.
Bleomycin
B. Cisplatin
C. Cyclophosphamide
D. Doxorubicin
ANSWERS
Question 1:
BIO GP
A newborn presents
with severe acidosis, vomiting, hypotonia, and neurologic deficits. Serum
analysis reveals elevated levels of lactate and alanine. These observations
suggest a deficiency in which of the following enzymes?
A.
Alanine aminotransferase
B. Glutamate dehydrogenase
C.
Lactate dehydrogenase
D. Pyruvate carboxylase
E. Pyruvate
dehydrogenase
The correct
answer is: E.
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Description: |
Question
2: BESCI GP
A group of
patients with lung cancer is matched to a group of patients without lung
cancer. Their smoking habits over the course of their lives is compared. Based on
this information, researchers compute the rate of lung cancer in patients who
smoke versus those who never smoked. This is an example of
A. case-control study
B. cohort
study
C. cross-sectional study
D. longitudinal
study
E. randomized control study
The correct answer is:
A.
|
Description: |
Question 3:
PHARM GP
A
pharmacologist is examining a new drug with potential sedative properties. He
begins by analyzing the pharmacokinetic properties of the drug. Studies of the
drug's rate of elimination yield the above data. Which of the following drugs
has similar kinetics to the drug being studied?
A.
Carbamazepine
B. Cimetidine
C. Ethanol
D.
Ketoconazole
E. Phenobarbital
. The correct answer is:
C.
|
Description: |
Question 4:
PATH ENDO
A 46-year-old
woman presents to her doctor complaining of weakness and fatigue. On physical
examination, her physician notices a 10-pound weight gain since her last visit 6
months ago. Her blood pressure is 160/100 mmHg. Blood tests reveal serum Na+ 155
mEq/L, K+ 2.8 mEq/L, and a decreased serum renin. Which of the following is the
most likely diagnosis?
A. Cushing's syndrome
B.
Diabetes mellitus
C. Pheochromocytoma
D. Primary
aldosteronism
E. Secondary aldosteronism
Correct, you answered
D.
|
Description: |
Question 5:
IMMU GP
A 38-year-old woman complains of cold, painful fingertips, as
well as difficulty swallowing and indigestion. Physical examination is
remarkable for a thickened, shiny epidermis over the entire body, with
restriction of movement of the extremities, particularly the fingers, which
appear claw-like. Which of the following autoantibodies is likely to be found in
this patient's serum?
A. Anti-DNA topoisomerase I
(anti-Scl-70)
B. Anti-double-stranded DNA (ds
DNA)
C. Anti-IgG
D. Anti-Sm
E.
Anti-SS-A
The correct answer is:
A.
|
Description:
|
Question 6:
BIO GP
A 26-year-old woman
and her 29-year-old husband have been trying to have a child for the last 3
years. During this time the woman has had 5 spontaneous abortions. The
karyotypes of the mother, father, and the most recently aborted fetus all
contained 46 chromosomes, and all pairs were normal except for the pairs shown
below.
The
event that led to the child's abnormal karyotype was:
A. adjacent
I segregation
B. adjacent II segregation
C. alternate
segregation
D. a recombination event within a paracentric
inversion
E. a recombination event within a pericentric
inversion
You answered D. The correct answer is:
B.
|
Description: |
Segregation from a quadrivalent ring results in three
different patterns of 2 x 2
segregation.
- Adjacent I: aneuploid gametes that are expected to
produce zygotic lethality
- Adjacent II: aneuploid gametes that are expected to
produce zygotic lethality
- Alternate: euploid gametes, 1/2 structurally normal,
1/2 translocation
Translocations in man:
1.
Down’s syndrome is caused by trisomy #21, and usually stems
from primary or secondary non-disjunction. Thus,
2n = 46N vs 2n = 47D
2.
About 5% of Down’s individuals are 2n = 46D, and all 2n = 46D
individuals have one parent that is 2n = 45N, i.e.,
2n = 46N vs
2n = 46D vs 2n = 45N
3.
Chromosome studies indicated involvement of chromosomes #15
and #21, and based on observations of “standard” (normal) karyotypes, a
non-reciprocal translocation between chromosomes #15 and #21 was hypothesized to
be responsible for the 2N = 46D individuals.
a)
One product of the translocation (the 15/21 chromosome)
contained most or all of the euchromatin of both chromosomes; whereas the
reciprocal product (the 21/15 chromosome) contained mostly heterochromatin and a
chromosomal NOR. Loss of the 21/15 chromosome thus was not expected to
have phenotypic consequence.
b)
Matings between a 2n = 45N (translocation heterozygote) and a
2n = 46N normal individual would thus yield…
2/3
aneuploid gametes: zygotic lethality except for the 2n =
46D
1/3
euploid gametes: normal zygotes, one of which is a translocation
heterozygote
i)
Note that the tendency to have Down’s children can be inherited.
ii)
Note also that translocations between D group (#13-#15)
and G group (#21, #22) chromosomes in humans occur much more frequently than
translocations between all other chromosomes in the human
complement.
(a) Because both D and G group
chromosomes in the human complement carry NORs, exchanges may arise between
“homologous regions” of “non-homologous” chromosomes, and may represent a
“price” for the existence of multiple NOR-bearing
chromosomes.
Question 7:
ANAT GI
A 70-year-old woman
undergoes a gastrectomy for Zollinger-Ellison syndrome. Her doctor informs her
that she will need to take intramuscular vitamin B12 shots for the rest of her
life. Absence of which of the following cell types is
responsible for this vitamin replacement requirement?
A. Chief
cells
B. G cells
C. Goblet cells
D. Mucous neck
cells
E. Parietal cells
Correct, you answered
E.
|
Description: Cholecystokinine =I cell of duodenum and
jejunum Secretin = s cell
duodenum Somatostatin = d cells in pancreatic islets, gi
mucosa |
Introduction
to Glandular Tissue
Glands are organized arrangements of secretory cells. All exocrine glands (and also most endocrine glands), are composed of epithelial tissue.
Although most glands give the appearance of being "solid" tissue, their epithelial nature is expressed by the organization of their cells, with each cell attached laterally to its neighbors. Every exocrine secretory cell has some portion of its plasma membrane exposed to an external surface, communicating with the outside of the body by a system of ducts.
In most
glands, the secretory cells are organized into secretory units, which are
described according to their shape as tubules, acini, or
cords.
Click here to see an example of a very simple gland, from frog skin.
BASIC TERMINOLOGY
Histologically, glands are described using some standard vocabulary, with which you should be familiar.
Simple / Compound
The simple / compound distinction is based on on duct shape.
A
simple gland has an unbranched duct (or
no duct
at all). There is only a single secretory unit (acinus or tubule).
Examples include sweat glands, gastric glands,
intestinal
crypts, and uterine glands.
A compound
gland has a branching duct. Salivary
glands and pancreas
are familiar examples. Compound glands are typically fairly bulky and
contain very many individual secretory units (acini or tubules).
Random tissue sections seldom show ducts branching. Nevertheless, the appearance of multiple duct profiles, in various sizes, provides evidence of a branching duct system.
Each secretory unit of a gland consists of cells arranged into an acinus, a tubule, or a cord. Each of of these arrangements has a different and characteristic appearance when viewed in section.
An acinus (from Latin, grape) is a small ball of secretory epithelial cells containing a tiny central lumen. Acini are usually formed by serous cells. [Acini are sometimes called alveoli, from L., small cavity.]
A typical
acinar cell is shaped like a pyramid. Its basal surface,
located at periphery of the acinus, rests on the basement membrane separating
the acinus from the underlying stroma. Its
lateral surfaces (the sides of the pyramid) are attached to adjacent
secretory cells. Its apical surface is free and faces the acinar
lumen, which communicates by duct with
the outside. The acinar cell's cytoplasm is also visibly
polarized, usually with basophilic basal cytoplasm and variously-staining
secretory granules concentrated in apical cytoplasm. For more, see serous cells.
A compound acinar gland can be quite accurately modelled as a bunch of grapes embedded in Jello™. The grapes are the acini, the branching stems are the ducts, and the Jello™ represents the rest of the stroma. Major and minor branches of the bunch represent lobes and lobules, respectively, separated by greater amounts of connective tissue.
In routine tissue sections, most acini are cut in random
planes and look like solid lumps, made of cells having various sizes and shapes.
The lumen of an acinus is typically tiny (i.e., much smaller than a
cell) and so is visible only when an acinus is sliced neatly across the middle.
In such a slice, the cells look like slices of pie, with the lumen in the
center.
Secretory
cells may also arrange themselves into secretory tubules (in contrast to
the small balls of cells which comprise secretory acini).
Sweat
glands are probably the most familiar tubular glands. Other tubular
glands include gastric glands
(in the lining of the stomach), uterine glands, and
various mucous
glands of the GI
system.
Because tubules are elongated, random sections commonly include the lumen as well as the secretory cells themselves (in contrast to the situation with acini). But interpretation of the sectioned appearance of tubular glands will depend on whether the tubules are simple or branched, on whether they are straight or twisted, and on whether or not adjacent tubules lie parallel to one another.
Cords are
arrangements of cells attached to one another to form sheets. In section,
the predominant pattern appears linear, even though the lines may twist and
branch.
Cords are a common arrangement for epithelial cells that are specialized for endocrine secretion. The cells retain an epithelial character, attached to neighboring cells, even though they may no longer comprise a surface barrier between interstitial space and a secretory lumen that leads to the outside. Examples of endocrine cells arranged into cords include the epithelial cells of pancreatic islets, parathyroid, adrenal cortex, and liver.
The liver (in the thumbnail above) is notable for having cells arranged into cords in spite of its major exocrine function. In order to maintain communication with ducts, the liver cords contain a network of intercellular channels called bile canaliculi.
Endocrine / Exocrine
The suffix -crine refers to secretion; the prefix endo- or exo- tells where the secretory product goes.
The product of exocrine glands leaves the body proper, either by direct secretion onto the body's surface (e.g., sweat) or into the lumen of an organ (e.g., gastric juice) or else by flowing through a system of ducts (e.g., saliva, pancreatic enzymes, bile). The cells of exocrine glands are generally arranged into secretory units in the form of acini or tubules (although the liver has a remarkable arrangement of cords).
The product of endocrine glands is secreted into interstitial fluid and hence into capillaries and general circulation. The cells of endocrine glands are often arranged into cords adjacent to capillaries or sinusoids.
Serous / Mucous / Mixed
The serous /
mucous
distinction is based on the secretory cell's product -- whether it is a
clear, watery solution of enzymes (serous,
like serum) or else a glycoprotein mixture (mucous,
like mucin). These two categories of secretory products come from
two distinct categories of cells, each with a characteristic appearance.
Mixed glands
(e.g., most salivary
glands) contain both types of cells. Glands which contain only
one of these two cell types may be described either as serous glands
(e.g., parotid
gland or pancreas)
or as mucous glands (e.g., Brunner's
glands).
Serous cells
are specialized to secrete an enzyme solution. Examples include serous cells of
the salivary
glands, exocrine cells of the pancreas,
gastric chief
cells, and Paneth cells of
intestinal crypts.
Serous cells of the pancreas and the salivary glands are typically
organized into secretory units called acini.
In routine light microscopy, serous cells are distinguished by basophilic basal cytoplasm, a centrally-located nucleus, and variously-staining secretory vesicles (zymogen granules) in apical cytoplasm. These features are all associated with organized mass production of protein for export. More.
Cells which
are specialized to secrete mucus are called mucous cells. Examples
include secretory cells of the salivary
glands, esophageal glands,
stomach
surface, pyloric glands,
and Brunner's
glands of the duodenum. These cells are typically organized into tubular secretory
units.
Goblet
cells are mucous cells which stand alone within the intestinal
epithelium. Goblet cells take their name from their characteristic shape,
with a broad opening at the apical end and a narrow, "pinched" base. Cells
with this goblet shape are also characteristic of the respiratory tract and
the female reproductive tract.
In routine light microscopy, mucous cells are most conspicuously distinguished by "empty"-appearing (i.e., poorly stained) apical cytoplasm and by densely-stained, basal nuclei. More.
Ducts
Ducts are
relatively simple tubular structures which are (usually) easily distinguished
from blood vessels by their conspicuous cuboidal to columnar epithelial lining.
Blood vessels, in contrast, are lined by simple squamous endothelium.
The glandular cells which comprise ducts generally receive much less attention than those which actually secrete the gland's product. However, the complete understanding of a gland requires some awareness of and attention to the duct system through which it drains. Ducts are not just passive "plumbing". Some duct segments actively modify the secretory product passing through, concentrating it by removing water).
For the purpose of describing duct structure and function, especially in compound glands which include branching ducts of various sizes and appearances, some special terminology can be useful. (By and large, the distinctions that these terms allow represent minor details rather than essential knowledge.)
Intercalated / Striated
Intercalated ducts are small ducts which drain individual secretory units. These are usually inconspicuous, lined by a simple epithelium consisting of low cuboidal cells.
In some
glands, intercalated ducts lead to striated ducts lined by a simple
epithelium consisting of conspicuous cuboidal to columnar cells. In the
basal cytoplasm of these cells, fine striations are visible at high
magnification.
The cells of the striated ducts are specialized for concentrating the secretory product that is flowing duct. They do this by pumping water and ions across the duct epithelium, from the duct lumen and into interstitial fluid. This striated duct function is carried to extremes in the proximal and distal tubules of the kidney.
Ultrastructurally, striated duct cells display extensive infoldings of the basal membrane. These folds are closely associated with mitochondria that provide ATP for the membrane pumps. In light microscopy, the basal folds and mitochondria are sometimes visible as basal striations, hence the name striated duct.
Secretory / Excretory
Both intercalated and striated ducts are sometimes called secretory ducts. They are located within lobules (intralobular). More distal ducts (interlobular), sometimes called excretory ducts, are generally passive conducting tubes. Their size varies, depending on how many branches have converged proximally. Larger excretory ducts may be lined by stratified cuboidal epithelium.
It is sometimes convenient to refer to ducts by location within the gland. The following terms are all directly descriptive. Intra- means within. Inter- means between. Lobes and lobules are clusters of secretory units served, respectively, by major and minor branches of the duct tree. Within a lobule, individual secretory units are separated from one another by little more than basement membranes and capillaries. In contrast, the stroma which separates lobules and lobes consists of thicker septa of connective tissue. (The distinction between lobes and lobules is arbitrary; lobes are evident upon gross inspection while lobules are evident to low power microscopy.)
Intralobular
-- Located within lobules, with no more connective tissue intervening
between ducts and secretory units (i.e., acini or tubules) than between adjacent
secretory units. Intercalated and
striated ducts
are intralobular.
Interlobular -- Located between lobules, within the thin connective tissue septa that separate lobules. All interlobular ducts are excretory.
Interlobar -- Located between lobes, within conspicuous, thick connective tissue septa that separate lobes. All interlobar ducts are excretory.
Parenchyma / Stroma
The parenchyma of an organ consists of those cells which carry out the specific function of the organ and which usually comprise the bulk of the organ. Stroma is everything else -- connective tissue, blood vessels, nerves, and ducts.
In most glands, the parenchyma consists of secretory epithelial cells. However, the parenchyma / stroma distinction can be convenient for describing not only glands but also other organs and even tumors. Examples:
· Cardiac muscle cells comprise the parenchyma of the heart. Everything else is stroma.
· Nephrons comprise the parenchyma of the kidney. Everything else is stroma.
· Hepatocytes comprise the parenchyma of the liver. Everything else is stroma.
· Neurons comprise the parenchyma of the brain. Everything else is stroma.
· Cancer cells comprise the parenchyma of malignant neoplasms. Everything else is stroma.
Because parenchyma often seems more interesting, stroma is commonly ignored as just boring background tissue. But no organ can function without the mechanical and nutritional support provided by the stroma. In any gland, connective tissue and capillaries of the stroma envelope every acinus, tubule, or cord, although they are often inconspicuous.
Pay attention to the stroma. If an organ is inflamed, the signs of inflammation appear first in the stroma.
Specialized Cells of the GI System
The GI system includes a number of highly specialized cell types, each differentiated to perform a specific function.
Most of the listed cells are epithelial, since variously specialized epithelia carry out most of the functions which are specific to the GI system. Other tissues are also vitally important to GI function, but are basically similar in all organ systems and are not individually listed here. See separate pages for smooth muscle, for cells of connective tissue (including immune system), and for nerve cells.
Listing of Cells by Region
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Listing of Cells by Function
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Listing of Cells by Name
Intestinal Absorptive Cells
Absorptive cells, or enterocytes, are the predominant cell type in the epithelium of the small intestine and colon. These cells are specialized for absorption of nutrients across the apical plasma membrane and export of these same nutrients across the basal plasma membrane. Upon release at the basal end of the cell, nutrient molecules diffuse into connective tissue space and eventually into capillaries or lacteals of the lamina propria.
The apical
surface area of each absorptive cell is greatly increased by evagination
into a dense array of microvilli, visible microscopically as the brush
border.
In the small intestine, brush border enzymes contribute to digestive breakdown (these enzymes are lacking from absorptive cells of the colon).
The microvilli are supported by an underlying meshwork of microfilaments which comprise the terminal web. At the lateral edges of each cell, the the terminal web reinforces the junctional complex that attaches adjoining cells. (This site is sometimes visible microscopically as a terminal bar at the apical corners of each cell.).
A pale (poorly stained) region above the nucleus indicates the location of the Golgi apparatus, where some absorbed nutrients are processed for transport.
Associated cell types: Interspersed among the many absorptive cells of the intestinal epithelium are scattered goblet cells, occasional enteroendocrine cells (which are difficult to distinguish in routine preparations), and occasional wandering cells of the immune system (e.g., lymphocytes, eosinophils).
The life-span of
absorptive cells is short, only a few days. During this time, the
cells migrate from deep in crypts, where they are formed by dividing stem cells,
to the surface epithelium where they eventually undergo apoptosis. Along
villi, this migration is sometimes called "the epithelial escalatory".
Look for apoptosis at the tips of villi.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
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Goblet cells
Goblet cells are scattered among the absorptive cells in the epithelium of the small intestine and colon. These cells are specialized for secretion of mucus, which facilitates passage of material through the bowel. The name "goblet" refers to the cell's shape, narrow at the base and bulging apically.
(Similar cells may also be found in the respiratory and reproductive tracts.)
The apical end of
each goblet cell is occupied by a large mass of mucus, which compresses
adjacent cells (thus conferring the characteristic "goblet" shape) and displaces
the nucleus toward the basal end of the cell. As in other mucous
cells, the nucleus is compact and intensely-stained.
Goblet cells comprise an integral part of the epithelium, attached by junctional complexes (evidenced in light microscopy as the "terminal bar") to adjacent absorptive cells.
The proportion of goblet cells to absorptive cells increases along the entire length of the bowel, with relatively few in the duodenum and very many in the colon. The colonic epithelium gives the superficial impression of being almost entirely goblet cells, but there are still several times as many absorptive cells. The goblets are just more conspicuous, with their bulging mucus droplets.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
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Mucous cells
Cells which
are specialized to secrete mucus are called mucous
cells. In routine light microscopy, mucous cells are
most conspicuously distinguished by their "empty" appearance (i.e., poorly
stained cytoplasm) and densely-stained, basal nuclei.
The nucleus in a typical mucous cell gives the impression of having been displaced and compressed by the mass of mucus accumulated in the apical end of the cell.
Mucus does not stain well with standard acidic or basic dyes, but is demonstrated with the Periodic Acid Shiff procedure (PAS stain).
Examples of
mucous cells from the GI may be found in salivary
glands, esophageal glands,
stomach
surface, and Brunner's
glands of the duodenum.
Goblet
cells, which stand alone within a surface epithelium, are a characteristic
feature of the intestine (as well as
the respiratory tract and the female reproductive tract).
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
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Serous Cells
Serous cells,
exemplified by pancreatic acinar cells, are specialized for exocrine
enzyme secretion.
A serous cell's cytoplasm is visibly polarized, with basophilic basal cytoplasm and variously-staining secretory vesicles (zymogen granules) concentrated in apical cytoplasm. The basal basophilia is due to a concentration of protein synthetic organelles (ribosomes on rough endoplasmic reticulum). The Golgi apparatus is usually located midway along the cell, typically in a supranuclear position.
Examples of serous cells include acinar cells of pancreas and salivary glands, gastric chief cells, and intestinal Paneth cells.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
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Paneth cells
Paneth cells
are secretory cells located at the ends of intestinal crypts.
The function for these cells is secretion of anti-bacterial proteins into
the crypt lumen, thereby providing protection for the stem cells
which line the crypt walls.
Paneth cells have typical serous-secretory appearance, with basophilic basal cytoplasm (containing protein-synthetic rough endoplasmic reticulum) and apical secretory vesicles (zymogen granules).
The secretory vacuoles of Paneth cells contain lysosomal enzymes, with anti-bacterial function.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
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Myoepithelial cells
Myoepithelial cells are contractile epithelial cells which forcibly express the contents of a gland. Although myoepithelial cells function like smooth muscle, they are typically located within a glandular epithelium, between the secretory cells and the basement membrane. Each myoepithelial cell has long cytoplasmic processes which wrap around a secretory unit. Hence, contraction of the myoepithelial processes can squeeze secretory product from the secretory unit into its duct.
Myoepithelial cells contribute significantly to the secretory activity of sweat glands, salivary glands, and mammary glands.
In routine histological preparations, myoepithelial cells are inconspicuous. The cell body can sometimes be noticed as an "extra" nucleus beneath some secretory cells. The contractile process are thin eosinophilic strands. In routine H&E stained sections of sweat glands, these can often be seen as small pink triangles underlying the secretory cells. In sweat glands and mammary glands, myoepithelial processes are normally difficult to observe without special stains.
· For a nice image of myoepithelial cells (in breast) stained with immunoperoxidase, see WebPath.
Consult your histology textbook and/or atlas for additional detail and micrographs of these cells
The sensation of taste is mediated by elongated sensory cells which occur in clusters called taste buds on fungiform and circumvallate papillae of the tongue. Taste buds interrupt and extend across the tongue's stratified squamous epithelium.
These sensory cells are normally replaced every 10-14 days by division and differentiation of stem cells, which is handy since they are exposed and easily damaged (e.g., by a bite of too-hot pizza).
Associated cell types: In addition to sensory cells, the elongated cells of the taste bud include support cells, which are sometimes (rather pretentiously) called sustentacular cells (from the same root as "sustain"). Stem cells are normally visible in taste buds as shorter cells with round nuclei which appear at the basal end of the tastebud.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells
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Hepatocytes
Although all cells are general-purpose metabolic factories, most mature cell types are functionally specialized to play one particular role in the economy of the larger body. In contrast, hepatocytes of the liver are remarkable for the breadth of their "specialization". Among other functions, hepatocytes:
· form and secrete bile
· store glycogen and buffer blood glucose
· synthesize urea
· metabolize cholesterol and fat
· synthesize plasma proteins
· detoxify many drugs and other poisons
· process several steroid hormones and vitamin D
The cellular structure of hepatocytes is correspondingly rich. Instead of displaying a concentration of one particular organelle, hepatocytes have lots of everything -- lots of mitochondria, lots of ribosomes, lots of Golgi bodies, lots of endoplasmic reticulum (both rough and smooth), lots of stored glycogen, lots of lysosomes, lots of plasma membrane (with microvilli on the free surface). They even have lots of nucleus (yes, hepatocytes may be polyploid and commonly have two full-size nuclei).
When an introductory biology book illustrates "the cell", the representative example is often a hepatocyte -- because hepatocytes offer splendid and numerous examples of most cellular organelles.
In appearance, hepatocytes are boxy
(cuboidal) cells with one or two large euchromatic nuclei and with abundant,
grainy cytoplasm that stains well with both acid and basic dyes (reflecting the
abundance of various cellular constituents). Because individual liver
cells have an indefinite lifespan, they may accumulate abundant lipofuscin (yellow-brown
"wear-and-tear" pigment), especially with advancing age.
Hepatocytes
are arranged into cords, in
which each hepatocyte is attached to its neighbors in a two-dimensional sheet.
On either side of the cord, each hepatocyte faces the space of Disse,
across which it communicates freely with adjacent sinusoids.
Hepatocytes are epithelial, but their epithelial nature is expressed in a rather peculiar way.
An ordinary epithelial cell sits on its basal surface, has an apical surface exposed to the external space, and is attached to its neighbors along its lateral surface. In principle, hepatocytes follow this same plan -- but they have a unique topology.
A typical hepatocyte has two
basal surfaces, on opposite ends of the cell where it faces the sinusoids on
either side of the cord in which it resides.
The apical surface of a hepatocyte occurs along a band around the cell's middle, half-way between the opposing basal surfaces. It is across this surface that bile is secreted. The edges of this apical surface are attached by junctional complexes to those of adjacent hepatocytes, thereby forming the bile canaliculi. These bile canaliculi form a network encircling each hepatocyte and sealed within the hepatic cord. Along this network (which is shaped like chicken-wire), bile can seep toward the periphery of the lobule and hence into the proper bile ducts which are found only portal areas.
(Bile canaliculi are barely visible in routine microscopic preparations, at sites where the boundary between adjacent hepatocytes has been cut neatly and perpendicularly. They can be clearly demonstrated with special stains.)
The lateral surfaces of a hepatocyte take the form of two broad bands which wrap around the cell between the two basal surfaces, separated by the narrow band of apical surface. These lateral surfaces attach the cell to its neighbors within the cord, with junctional complexes sealing off and separating the bile canaliculi (at the apical surface) from the plasma-containing space of Disse (at the basal surfaces).
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
Endothelial Cells
Endothelial cells are simple squamous cells which line the entire vascular system (including lymphatic channels). Endothelial cytoplasm is inconspicuous in routine light microscopy. Typically only the nuclei are visible, at the boundary between the lumen and the wall of a vessel.
Endothelial nuclei typically appear thin and dark, in cross section. However, occasionally endothelium lies parallel to the plane of section. In this case the nuclei may appear very large, round, and pale.
Although endothelial cells appear rather uninteresting under the microscope, these are important cells. They are situated at a critical location, between the blood and all other body cells. They secrete substances which control local blood flow and blood coagulation, and they are active participants in white blood cell emigration during inflammation.
Continuous endothelium. Throughout much of the body, the capillary endothelial lining is continuous, with neither large gaps between cells nor holes through cells. Materials pass through the endothelium either by diffusion or via rapid vesicular transcytosis. (In most of the brain, a lack of transcytotic vesicles accounts for the blood brain barrier -- the only substances which cross such a barrier are those which can diffuse through plasma membranes or those for which specific membrane channels exist.)
Fenestrated endothelium. In a few special locations -- notably in the sinusoids of the liver, in the glomeruli of the kidney, and in most endocrine glands -- the endothelium is fenestrated (i.e., full of holes -- from fenestra, window). In the liver, where there is also no basement membrane, the fenestrations permit blood plasma to wash freely over the exposed surfaces of the hepatocytes through the space of Disse.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
Kupffer Cells (Liver Macrophages)
Kupffer cells are macrophages found in the sinusoids of the liver. These cells have standard macrophage / monocyte specialization (i.e, receptor-mediated phagocytosis, lysosomal digestion). This particular population of macrophages are especially significant, with responsibility not only for cleaning bacteria out of the portal blood stream (the "dirty" blood" from the intestine), but also for removing worn-out red blood cells and recycling hemoglobin (a job shared with macrophages of the spleen).
Kupffer cells
are closely associated with the endothelial lining of the liver. Lying
along side or draped across the liver sinusoids, the Kupffer cells are not
easily distinguished from the endothelial cells.
Historical note: The term reticuloendothelial system refers to the macrophages of the liver, spleen and lymph nodes, i.e., those organs with elaborate endothelially-lined channels supported by reticular connective tissue. The name reflects former confusion about the distinction between endothelial cells and the scattered population of macrophages (monocytes, histiocytes). Macrophages can be readily labelled experimentally through their phagocytosis of injected carbon particles. However, endothelial cells are also labelled by the same procedure. Although endothelial cells are not dramatically phagocytotic, they do shuttle some materials across the endothelial lining via small endocytotic and exocytotic vesicles.
Consult your histology textbook and/or atlas for additional detail and electron micrographs of these cells.
Gastric Surface Mucous Cells
The
protective cells which line the surface of the stomach (including gastric pits) are
called surface mucous cells. These cells are critical for resisting
attack by digestive acid and enzymes.
Any disruption of these cells' function can lead to an ulcer. See WebPath (low mag), WebPath (high mag), or Milikowski & Berman's Color Atlas of Basic Histopathology, pp. 240-241.
The
appearance of surface mucous cells is rather different from that other mucous
cells
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Endocrine
Cells Many of
the body's cells secrete substances which influence other cells, either locally
or at some distance. Cells generally regarded as endocrine cells are those
which are conspicuously specialized for this function. Pancreatic islets are covered elsewhere. Consult
your histology or cell biology textbook for additional information about stem
cells.
Parietal cells
(oxyntic
cells) of the stomach secrete acid,
by pumping hydrogen ions across the cell membrane. These are among the
most dramatically differentiated epithelial cells in the body, with functional
specialization
reflected in their microscopic appearance.
Chief cells of the stomach secrete the
digestive enzymes (pepsins) of the stomach and have typical serous-secretory
appearance.
Mucous neck
cells of
the stomach are
inconspicuous cells with a typical mucous-secretory
appearance. These cells are most common in the upper ("neck") region of
the fundic glands (i.e., near to the glands' openings into the bottoms of gastric pits).
Their specific function remains unclear. Mucous neck
cells are difficult to identify in routine sections of stomach mucosa. When the
cells are neatly cut from top to bottom, they can be recognized by the basally
compressed (often wedge-shaped) nucleus and the stored mucus that fills the
apical cytoplasm. But in other random planes of section, the
poorly-stained mucus is inconspicuous and the nucleus can resemble any of the
small dense nuclei found in lamina
propria.
Link to the endocrine
system.
The gastrointestinal system
has two classes of such cells, the islets of Langerhans in
the pancreas
and the enteroendocrine cells in the mucosal epithelium of the stomach and intestine.Microscopically,
stem cells lack distinguishing characteristics. However, their activity
can be detected by the presence of mitotic figures, the intensely basophilic
masses of condensed chromation which characterizes cells undergoing mitosis.
Stem cells of the intestinal mucosa line
the walls of the crypts and
continually replenish the intestinal epithelium, completely replacing all the absorptive
cells and goblet
cells approximate once every four days. These cells are inconspicuous
when resting, but mitotic figures (intensely basophilic condensed chromatin) are
common and easily noticed in the crypts of the small intestine.
- Yersiniosis
is an infectious disease caused by a bacterium of the genus Yersinia. In the
United States, most human illness is caused by one species, Y. enterocolitica.
Infection with Y. enterocoliticacan cause a variety of symptoms depending on
the age of the person infected. Infection with Y. enterocoliticaoccurs most
often in young children. Common symptoms in children are fever, abdominal
pain, and diarrhea, which is often bloody. Symptoms typically develop 4 to 7
days after exposure and may last 1 to 3 weeks or longer. In older children and
adults, right-sided abdominal pain and fever may be the predominant symptoms,
and may be confused with appendicitis. In a small proportion of cases,
complications such as skin rash, joint pains, or spread of bacteria to the
bloodstream can occur.
- Y.
enterocoliticabelongs to a family of rod-shaped bacteria. Other species of
bacteria in this family include Y. pseudotuberculosis, which causes an illness
similar to Y. enterocolitica, and Y. pestis, which causes plague. Only a few
strains of Y. enterocoliticacause illness in humans. The major animal
reservoir for Y. enterocoliticastrains that cause human illness is pigs, but
other strains are also found in many other animals including rodents, rabbits,
sheep, cattle, horses, dogs, and cats. In pigs, the bacteria are most likely
to be found on the tonsils.
- Infection
is most often acquired by eating contaminated food, especially raw or
undercooked pork products. The preparation of raw pork intestines
(chitterlings) may be particularly risky. Infants can be infected if their
caretakers handle raw chitterlings and then do not adequately clean their
hands before handling the infant or the infant’s toys, bottles, or pacifiers.
Drinking contaminated unpasteurized milk or untreated water can also transmit
the infection. Occasionally Y. enterocoliticainfection occurs after contact
with infected animals. On rare occasions, it can be transmitted as a result of
the bacterium passing from the stools or soiled fingers of one person to the
mouth of another person. This may happen when basic hygiene and handwashing
habits are inadequate. Rarely, the organism is transmitted through
contaminated blood during a transfusion.
- Y.
enterocoliticainfections are generally diagnosed by detecting the organism in
the stools. Many laboratories do not routinely test for Y. enterocolitica,so it is important to notify laboratory personnel when
infection with this bacterium is suspected so that special tests can be done.
The organism can also be recovered from other sites, including the throat,
lymph nodes, joint fluid, urine, bile, and blood.
- Uncomplicated
cases of diarrhea due to Y. enterocoliticausually resolve on
their own without antibiotic treatment. However, in more severe or
complicated infections, antibiotics such as aminoglycosides, doxycycline,
trimethoprim-sulfamethoxazole, or fluoroquinolones may be useful.
.
- Most
infections are uncomplicated and resolve completely. Occasionally, some
persons develop joint pain, most commonly in the knees, ankles or wrists.
These joint pains usually develop about 1 month after the initial episode of
diarrhea and generally resolve after 1 to 6 months. A skin rash, called
"erythema nodosum," may also appear on the legs and trunk; this is more common
in women. In most cases, erythema nodosum resolves spontaneously within a
month.
- Necrotizing
granuloma: The center of the granuloma consists of necrotic macrophages and
polymorphonuclear neutrophils. The walls of the granuloma are usually composed
of well defined macrophages and elongated macrophages (epithelioid). These
epithelioid macrophages or histiocytes often line up in a linear fashion that
is called palisading. This type of response is associated with certain
bacterial infections:
- Bernard-Soulier
Syndrome is a severe bleeding disorder. Bernard and Soulier described this
condition in 1948 when they identified a young man with a bleeding problem.
This patient had a prolonged bleeding time, a low platelet count and large
platelets. These features are the hallmark of the condition. Since the
original condition was described a large number of patients have been
identified with the syndrome. Although it is not exactly clear how many
patients suffer from the illness, it is thought to occur in about 1 in a
million patients. The purpose of this web-site is to gather information on the
syndrome and to facilitate physicians in making the diagnosis and informing
patients on the current status of research in the area.
- congenital
bleeding disorder familial - autosomal recessive chrom.#: 17pter-p12
characterized by thrombocytopenia and large platelets. The disorder was
recognized to be familial and inherited in an autosomal recessive manner. In
the 1970s, the molecular defect was shown to involve the absence of a platelet
membrane glycoprotein. BSS is one of a group of hereditary platelet disorders
characterized by thrombocytopenia, giant platelets, and a tendency toward
bleeding. Other disorders in this category are the May-Hegglin anomaly and
gray platelet syndrome.
- Platelets
are particles that circulate in the blood. Their primary role is to cause
clotting. When a platelet meets a damaged blood vessel, it tries to correct
this damage by clotting. Bernard-Soulier platelets are missing a part of the
platelet that is involved in the initial steps of a platelet forming a clot
and consequently patients with the syndrome have bleeding problems.
- The
problems Bernard-Soulier patients face are exemplified in the original
description of the young man described by Bernard & Soulier. The patient
suffered from bleeding problems from early childhood. For example following a
tooth extraction he had prolonged bleeding. He bled into his spinal cord and
had bruising to his eye following an accident. The patient died when he had a
brain haemorrhage following a fight.
- Hematological
Manifestations
- 1.
Bleeding
- 1. Skin
easy bruising, petechiae, purpura
- 2.
Mucous Membranes recurrent epistaxis, gingival bleeding menorrhagia
- 3.
Others excessive bleeding at the time of injury or
surgery
What
causes the bleeding problem?
- The
cause of the problem has been identified as due to an abnormality on the
glycoprotein Ib-IX-V complex on platelets. This is the receptor that causes
platelets to stick. When this receptor is absent, platelets cannot stick.
- What is
the glycoprotein Ib-IX-V complex and how does it work?
- The
glycoprotein Ib-IX-V complex (abbreviated to GPIb) is four proteins that stick
out of the surface of the platelet, the four proteins are termed GPIb alpha,
GPIb beta, GPIb-IX and GPV. The subunit GPIb alpha binds to a protein called
von Willebrand factor and this starts the clotting process. If the protein von
Willebrand factor is absent or abnormal this also leads to a bleeding problem.
The exact roles of GPIb beta, IX and V are not clear, but they seem to
function to support the role of GPIb alpha.
low
glycoprotein Ib, IX, and V levels
platelets
unresponsive to ristocetin in vitro
giant bizarre
platelets (mean diameter = 5-6 microns)
- Desmopressin
acetate (DDAVP) has been shown to shorten the bleeding time in some, but not
all, patients with BSS. It may be useful for minor bleeding episodes. The
exact mechanism for this is unknown, but it may relate to increased levels
of von Willebrand factor binding to some residual glycoprotein Ib in patients without an absolute deficiency.
- Recently,
recombinant activated factor VII has been used in patients with congenital
platelet disorders including BSS. Once again the exact mechanism of action
is unknown, but it may work by increasing thrombin generation and the
deposition of fibrin at the site of vascular injury.
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Safety for use during pregnancy has not been established.
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Documented
hypersensitivity; platelet-type von Willebrand disease
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Not
established, limited data exist; administer as in adults
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C -
Safety for use during pregnancy has not been established.
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BRANCHIAL
(PHARYNGEAL) CYSTS AND FISTULAS