SM01 Mini4 Flashcards
functions of blood
- transports O2, CO2, hormones, nutrients, & waste
- stabilizes pH & electrolyte concentrations of interstitial fluids
- regulation of blody temperature
- migration pathway for WBCs
What are the three formed elements of blood?
- erythrocytes (RBC)
- leukocytes (WBC)
- platelets
plasma
mostly water & plasma proteins (albumin, fibrinogen, immunoglobulins)
but also lipids, hormones, vitamins & salts
must be collected in blood tube with anticoagulant (heparin, EDTA, sodium citrate)
serum
plasma lacking fibrinogen
collected without anticoagulation
blood clot
fibrin strings connecting trapped blood cells
Wright stain
mixture of methylene blue & eosin
methylene blue
basic/positively charged dye
stains acidic/negatively charged cellular structures blue
ex. DNA, RNA, specific granules of basophils
eosin
acidic/negatively charged dye
stains basic/positively charged structures pink/red
ex. hemoglobin (not +, but stretches of + aa) & specific granules of eosinphils
azures
stain reddish blue when methylene blue is oxidized
ex. lysosomes
erythrocyte
RBC
function: transport of O2 & CO2
no nucleus or organelles
only has: plasma membrane, cytoskeleton, hemoglobin, & glycolysis enzymes
increase in # at higher altitude (decreased binding of O2)
8um diameter
hematocrit
percentage (v/v) of packed RBCs in given sample of blood after centrifugation
higher in males than females
erythropoietin
hormone
secreted by kidneys in adults; liver in fetus
stimulates RBC production to match O2 demand
What is the life span of an erythrocyte?
120 days
then phagocytosed in spleen, liver, or bone marrow→ hemoglobin recycled
Rouleaux
stacking of erythrocytes seen in capillaries
Why do erythrocytes have a biconcave shape?
to maximize their surface area to volume ratio→ maximize O2 exchange
anisocytosis
RBCs of unequal size
microcyte: less than 6um
macrocyte: greater than 9um
How do RBCs pass easily thru smaller blood vessels?
increased flexibility via spectrin
hereditary spherocytosis
somatic dominant inheritance
cause: defective spectrin or ankyrin
result: abnormal spectrin lattice binding or complete absence→ spherical RBCs instead of biconcave
RBCs are more fragile, break down rapidly & transport less O2
dendritic cells
differentiate from monocytes in tissue
best anitgen-presenting cells in body
granulocytes
have specific granules
differentiated by Wright stain rxns
neutrophils, eosinophils, & basophils
non-dividing terminal cells w/life span of days
agranulocytes
no specific granules
but do have nonspecific azurophilic granules (lysosomes)
lymphocytes & monocytes
Why do neutrophils have a mulitlobed nucleus?
aides in moving between tissues as they are more flexible
What are the main components of pus?
dead neutrophils & dead bacteria
function of neutrophils
first line defense of bacterial infection
sense chemical gradients near them
active phagocytosis of bacteria
neutrohils microscopy
identified by 3-5 lobed nucleus
Why do neutrophils use glycosis for ATP generation?
allows them to survive in anaerobic environment→ kill bacteria & clean up debris in poorly oxygenated regions (inflammed or necrotic
what is the life span of neutrophils?
6-7 hours in blood
1-4 days in connective tissue
chemoattractors
mediators of processes, including immune responses, inflammation, wound healing, & embryogenesis
attract cell type to their area of need
ex. C5a of complement system, intermediate lipid metabolites (arachidonic acids & leukotriene B4), N-formylated oligopeptides, & chemokines
chemotaxis
crawling along s soluble concentration gradient towards source of attractant
cell driven by lamellipodi
what does mitochondria release during necrosis that causes inflammation?
N-methylated oligopeptides
cytokine
non-antibody protein released by spefic cell type as part of body’s immune response
chemokine
cytokine that can induce chemotaxis of a leukocyte during inflammation
classic symptoms of inflammation
swelling, redness, heat, & pain
What is the purpose of acute inflammation?
ease travel of leukocytes & plasma proteins to injury site
chronology of acute inflammation
- increase blood flow via vasodilation
- loosening of capillary endothelial cell tight junctions
- emigration of leukocytes form microcirculation
diapedesis
passage of WBCs thru intact capillary walls into surrounding tissue
myeloperoxidase
in lysosomes of neutrophils
generates highly reactive hypochlorite & chloramines
neutrophil oxidative burst
azurophilic granules (lysosomes) & specific granules of neutrophils fuse w/phagosome
hypochloride from myeloperoxidase & superoxide denatures proteins & membranes of microorganisms→ kills them
toxicity of these rxns leads to neutrohil death
chronic granulomatous disease
inherited disorder of phagocytic cells
cause: defect in NADPH oxidase enzyme of phagocytes→ inability to produces superoxide anions O2- for denaturing/killing targets
result: recurrent life-threatening bacterial & fungal infections
granulomas develop due to chronic inflammation
cannot activate NETs
granuloma
localized nodular inflammation found in tissue
Where is collagenase in neutrophils & why do they have it?
in both specific granules & azurophilic
neutrophils will release collagenase in CT when they cannot reach their target→ collagenase breaks down collagen of CT→ neutrophil can pass thru
neutrophil extracellular traps
formed during cell death of neutrophils
creates network of chromatin & granule proteins that can bind & kill microorganisms
dependant on generation of reactive oxygen species by NADPH oxidase
more bacteria killed this way than by phagocytosis
eosinophil microscopy
bilobed nucleus
large, pink specific granules
functions of eosinphils
parasitic infections (generally multicellular)
phagocytosing antigen-antibody complexes
control mechanisms in allergy & asthma
parasite
organism that grows, feeds, & is sheltered on or in a different organism while not contributing to survival of host
eosinophil killing
can phagocytose or secret granules when target is too large for phagocytosis
agent: major basic protein
a lot of self-damage when secreted as it targets eukaryotes
internum
thick band seen on specific granules of eosinophils
produced by major basic protein
eosinophilia
increase # of eosinophils in blood
causes: parasitic infection OR allergic rxn
basophil microscopy
S-shaped nucleus
nucleus commonly masked by large dark blue specific granules
What do specific granules of basophils contain?
heparin & histamine
difference between basophils & mast cells
basophils- in blood
mast cells- in CT
functions of basophils
release of mediators: histamine, serotonin, prostaglandin, & leukotrienes
increases blood flow to area & adds to infammatory process
lymphocytes
subdivided: T, B, null (NK, stem, etc)
2nd most populace WBC behind neutrophils
more often in lymph than blood
only leukocyte that can return from tissue back to blood
What is the life span of a lymphocyte
few days- years
lymphocyte microscopy
1.5 size of erythrocyte
dense, round nucleus that takes up most of the cell
Monocyte functions
- phagocytosis
- destroy dead & defunct cells & antigen/foreign particulate matter
- immune response
- **precursor of macrophages (differentiate in CT)
monocyte microscopy
largest blood cell: 12-20um (3x erythrocyte)
large, kidney-shaped nucleus
macrophage
differentiates from monocyte when it enters CT
connective tissue surrounding it will determine exact final differentiation
platelets
aka thrombocytes
pieces derived from megakaryocyte
life span= 10 days
no nucleus, but do have lysosomes, mitochondria, ER, Golgi, 3 types granules, & *extensive cytoskeleton*
megakaryote
giant precursor cell of platelets
never leaves bone marrow, but reaches appendages out into the blood stream
function of platelets
- prevent excessive internal or external bleeding after injury
- activated on exposure to collagen
- secrete platelet-derived growth factor & transforming growth factor beta→ promotes invasion of fibroblasts
von Willebrand factor
promotes adhesion of platelets to endothelial cells
produced by platelets & endothelial cells
platelet factor IV
stimulates blood coagulation
where is post-natal blood made and how does it change with age?
red bone marrow
of bones reduced w/age for relatively constant area of red bone marrow
in cancellous bone
how does the body respond to severe blood loss (to replace blood)?
transition of yellow bone marrow to red bone marrow
hematopoiesis
process of blood cell formation
yellow bone marrow
yellow due to adipose cells
seeded w/some hematopoietic cells
hematopoietic stem cell
multipotent cell
gives rise to all 3 formed elements in blood
mesenchymal stem cell
pluripotent
can differentiate into osteoblast, chondroblast, mycocyte, & others
how is the stem cell population kept constant?
only one daughter cell differentiates
totipotent
cell can differentiate into anything
pluripotent
blastocyst inner cell mass
can become all cell types except extra-embryonic
where is fetal blood made?
5+5
blood precursors from yold sac mesoderm
5W→ fetal liver
5M→ bone marrow
red bone marrow
colored red due to presence & formation of blood
bone marrow stroma
“land”
where blood cells develop
formed by reticular cells and the web of reticular fibers they create (much like fibroblasts)
also contains type I collagen, fibronectin, laminin, & proteoglycans
bone marrow sinusoids
blood vessels where mature blood cells enter blood stream
lined by endothelial cells w/discontinuous basal lamina
what do reticular cells secrete in the stroma?
reticular fibers (type III collagen)
cytokines that stimulate development of progenitor cells into blood cells
why is it important that the basal lamina of endothelium of bone marrow sinusoids be discontinuous?
it’s how the newly formed blood cells enter, between the endothelial cells
stages of lymphocyte development
hematopoietic stem cell→ lymphoid stem cell (CFU-L)→ T or B lymphocyte
CFU
colony forming unit
GEMM
granulocyte, erythrocyte, monocyte, megakaryocyte
should ahve one more M for Mast cells
What blood cell does not differentiate in bone marrow?
T lymphocytes migrate to & differentiate in the thymus
erythropoiesis
formation of RBCs
get smaller
nucleus condenses & eventually extrudes
loss of organelles
gain of hemoglobin
released into bloodstream as proerythroblast, takes 7 days to make one
what are the derivatives of the mesonepheric ducts?
males: vas deferens, seminal vesicle, & epididymis as induced by testosterone & eferent ductules
female: degenerate due to absence of testosterone
what is the testis-determining factor?
SRY protein
coded for by SRY gene
on Y chromosome
what embryonic layer are the gonads derived from?
intermediate mesoderm
genital ridges
formed by proliferation of coelomic epithelium & condensation of mesenchyme from mesonephric ridge
where do primordal stem cells originate?
epiblast of yolk sac wall
where do primordial stem cells migrate to? what happens when they fail?
genital ridge during W4-W5
invade sex cords W6
if they don’t→ gonads don’t develop
how are primitive sex cords formed?
epithelium proliferates & penetrates underlying mesenchyme in medulla of indifferent gonads
what do the primitive sex cords become?
male: testis cords (horseshoe shaped)→ seminiferous tubues containing primodial germ cells (outer portion) & rete testis tubular network (inner portion)
female: form irregular clusters w/oogonia as medullary cords, then degenerate
when does the tunica albuginea form?
coincides w/testis cord formation
origin & funtion of Leydig cells
mesenchyme between testis cords
testosterone secretion W8 as stimulated by hCG (human chorionic gonadotropin)
when does lumenization of the testis cords occur?
during puberty
location & function of sertoli cells
secretion of mullerian inhibiting substance (aka anti-mullerian hormone)
found in testis
what effect does mullerian inhibiting substance have?
suppresses development of paramesonephric ducts in males
where & when do the paranephric ducts form?
D44-48
longitudinal invaginations of surface epithelium later to mesonephric ducts
where do the paranephric ducts terminate & open?
on urogenital sinus between ends of mesonephric ducts
cranial opening into coelomic cavity
what forms the paradidymis?
caudal mesonephric tubules as they degerate
location: caudal end of epididymal connection to testis
what forms the appendix epididymis?
cranial mesonephric duct
location: cranial to efferent ductules & distal from testis relative to appendix testis
what are the derivatives of the paranephric ducts?
males: appendix testis (cranially) & prostatic utricle (distally)
females: uterine tubes, uterus, & upper vagina
what female structure is the prostatic utricle homologous with?
uterus & upper vagina
cortical cords
2nd generation of medullary cords in ovary development
w/oogonia
form in W7
what happens to the coritcal cords in M3?
split into isolated cell clusters
proliferate into primary oocyte surrounded by follicular cells
primordial follicle
primary oocyte surrounded by follicular cells
epoophoron
vestigial epigenital mesonephric ductules in females
homologous w/efferent ductules
paroophoron
vestigial caudal mesonephric ductules in females
homologous w/paradidymis
Gartner’s cyst
vestigial distal mesonephric duct in females
homologous to seminal vesicle
function & origin or estrogenic hormones in fetus
from mother & placenta
must be present for full development of female genital tract
how is the uterus formed?
fusion of lower portion of paramesonephric ducts & degeneration of septum
how is the vagina formed?
upper 1/3: fusion of distal paramesonephric ducts
lower part: posterior wall of urogenital sinus
sinovaginal bulbs
- induced to form by paramesonephric contact to urogenital sinus
- collection of endodermal cells from urogenital sinus
- proliferates into solid plate
- canalizes M5 into lower portion of vagina
unterine & vaginal formation abnormalities
- uterine duplication w/vaginal duplication
- uterine duplication w/o vaginal duplication
- uterine duplication w/o vaginal duplication only superiorly→ Y-shape
- septally separated uterus (unknown cause)
- one-sided: one paramesonephric dict fails to develop
- cervical atresia
proerythroblast
large cell
basophilic cytoplasm
visible nucleoli
NOT morphologically distinguishable from other committed precursor cells or myeloid stem cell
basophilic erythroblast
strongly basophilic cytoplasm→ caused by large # of ribosomes involved in synthesis of hemoglobin
NO visible nucleoli
polychromatophilic erythroblast
less polyribosomes→ less basophilic→ less blue
more hemoglobin in cytoplasm→ more acidophilic→ more pink
polychromatic b/c both colors present
orthochromatophilic erythroblast
nucleus condensation
loose basophilia→ uniform acidophilia
reticulocyte
AFTER expelling nucleus
still has a few polyribosomes→ agreggate to form reticular network
leaves bone marrow & passes to blood stream
lasts 2-3 days
what is the difference between reticulocytes & erythrocytes?
loss of polyribosomes & mitochondria
nurse cell
macrophage that erythrocytes develop on
phagocytose discarded nuclei of erythroblasts
what is distinguishable when a blood smear is stained w/cresyl blue?
reticular network of polyribosomes in reticular cells
what is the action of erythropoietin?
stimulates colony forming unit-erythrocyte differentiation
where is erythropoietin produced/secreted from?
endothelial cells of peritubular capillary network of kidneys
hepatocytes
granulopoiesis
development of granulocytes- eosinophils, basophils, & neutrophils
myeloblast
looks like lymphocytes, but has 3-5 nucleoli
1st stage of granulocytes after committed precursor
promyelocyte
azurophilic
very large
appearance of non-specific granules
2nd stage of granulocytes after committed precursor
myelocyte
oval or flat nucleus
specific granules
last stage cell division is possible
3rd stage of granulocytes after committed precursor
metamyelocyte
accumulation of specific granules
indented nucleus in C or V shape
4th stage of granulocytes after committed precursor
band/stab cell
rarely seen for basophils or eosinophils, mostly immature neutrophils
5th stage of granulocytes after committed precursor
what is an increased number of band cells in blood stream indicative of?
bacterial infection
what cell type is stored in bone marrow?
neutrophils (5:1 in blood stream)
what two WBCs share the same progenitor?
monocytes & neutrophils
promonocyte
bluish cytoplasm due to numerous azurophilic non-specific granules (lysosomes)
2nd stage after committed precursor
monoblast is between progenitor & this stage
monocyte
1010 made daily
1-2 days in circulation
then enter connective tissue where they differentiate into macrophages
leukemias
malignant clones of leukocyte precursors
found in lymphoid tissue & bone marrow
large release of immature cells into blood
result: lack of some cell types & excessive production of others
pt. usually anemic & prone to infection
megakaryocytopoiesis
nucleus becomes highly polyploid- 30X DNA, chromosomes replicate, but cells don’t divide
invaginations of plasma membrane form demarcation membranes w/platelet granules in each
platelets break off into bone marrow sinuses
what is contained in platelet granules?
platelet-derived growth factor, fibroblast growth factor, von Willebrand’s factor, & platelet factor IV
what is the function of von Willebrand’s factor?
promotes platelet adhesion to endothelial cells
how do erythrocytes enter sinusoids?
not sufficient motility like leukocytes
use pressure gradient: veins are smaller tha arteries in bone marrow, resulting in suciton of RBCs into capillary
which WBCs can divide after differentiation and which cannot?
divide: monocytes & lymphocytes
unable to divide: eosinophils, basophils, & neutrophils (granulocytes)
how are the testes attached cranially & caudally during descent?
cranially: as mesonephros degenerates urogenital mesentary attachment is limited to the cranial suspensory ligament
caudally: caudal genital/inguinal ligament→ gubernaculum
1st phase of testis decent
enlargment of testis
regression of mesonephros
cranial ligament regresses & releases testis (diaphragmatic connection)
2nd phase of testis descent
descent to level of inguinal ring by W12
3rd phase of testis descent
transinguinal descent
testes pass thru inguinal canal by W28
into scrotum by W33-38
guided by testosterone & gubernaculum (attached to scrotal floor
vaginal process
testis slides behind this extension of the peritoneal cavity
becomes tunica vaginalis
canal connecting it to peritoneum is obliterate at birth or shortly after
what happens when obliteration of vaingal process to peritoneum is incomplete or weak?
prone to indirect inguinal hernia
irregular can leave small cyst→ hydrocele of testis
descent of ovaries
cranial genital ligament→ suspensory ligament of ovary
caudal genital ligament→ ligament of ovary proper & round ligament of uterus
ovaries suspended in peritoneal fold→ broad ligament of uterus (remnant of gubernaculum)
settle just below rim of true pelvis
What are the connections of the round ligament?
uterus & labia majora
indifferent stage of external genitalia
W3-W7
mesenchymal cells from primitive streak around cloaca
form pair of genital folds extending to proctoderm (anus)
folds unite cranially to form genital tuberacle
genital swellings form laterally to folds
cloaca breaks down in W7→ opening of urogenital sinus between folds
adults structures from genital tubercle
males: glans penis
females: clitoris
adults structures from genital folds
males: shaft of penis
females: labia minora, urethral & vaginal orifices
adult structures from genital swellings
males: scrotum
females: labia majora
what hormone influences growth of male external genitalia?
dihydrotestosterone
male urethra formation
lateral folding & midline fusion of genital folds
endodermal in origin from urogenital sinus
penile raphe
epithelial seam alond penile shaft & scrotum where urethra fused
vestibule
opening to urethra & vagina in females
remnant of urogenital groove
hypospadias
most common male external genitalia malformation
ventral opening of urethra anywhere that isn’t at the glans
true hermaphrodite
have ovotestes (ovaries & testicular tissue in same gonad)
or in opposite gonad (one ovary & one testicle)- this type has NEVER been seen in humans
usually 46 XX w/hypertropied clitoris
female pseudohermaphrodite
has ovaries
ambiguous or male external genitalia
caused by fetal exposure to excessive andrgens→ clitoral enlargement & labial fusion
congential adrenal hyperplasia: excessive production of androgens by fetal adrenal glands
male pseudohermaphrodite
has testes
ambiguous or female external genitalia
cause: inadequate production or testosterone and/or MIF by fetal testies
androgen sensitivity syndrome
aka testicular feminization
genetic males 46 XY
have testes
normal females external phenotype
cause: lack of androgen receptors or failure of response to dihydrotestosterone
MIF functional so uterus & upper vagina NOT present
not diagnosed until seeking tx for amenorrhea
lymphoid follicle
aka lymphoid nodule
small spherical nodules arrangement of immune cells in connective tissue & inside organs
UNencapsulated
reticular fiber frame by reticular cells NOT ERCs
what is teh definitive difference between 1º & 2º lymphoid follicles?
if they have a germinal centrer→ 2º
2º are usually larger, but a large follicle can NOT be labeled 2º w/o germinal center
immunocompetence
ability of body to produce normal immune response w/exposure to antigen
naive lymphocyte
immunocompetent, but has yet to be exposed to antigen
structure of thymus
bilateral organ superior to heart
thin connective tissue capsule w/trabeculae that divides organ into lobules
how are thymic lobules established?
via trabeculae of connective tissue
why do the thymic lobules cortices stain darker?
they are richer in lymphocytes than medulla
after reaching immunocompetence in cortex, how do T cells enter the bloodstream?
migrate to medulla→ bloodstream
why is the thymic medulla lighter staining than the cortex?
less cells
95% precursor T cells die via apoptosis during + & - selction process in cortex
functions of epithelial reticular cells in thymus
- framework
- form cytoreticulum: ERCs connected together by desmosomes
- in cortex & medulla
- produce & secrete thymic hormones
- promote lymphocyte proliferation & maturation
- form blood-thymus barrier
why is it important to have a blood-thymus border?
to exclude antigen from developing thymocytes
antigen contact at this stage results in thymocyte apoptosis
what characteristics make ERCs like epithelial cells?
connected by desmosomes
contain keratin intermediate filaments
have basal lamina
what makes ERCs NOT like epithelial cells?
grow in reticular pattern
what is the embryonic origin of the thymus?
lymphocytes are mesoderm
epithelial reticular cells are endoderm
what 3 structures make up the blood-thymus barrier?
- thymic cortical epithelial cells joined by desmosomes
- dual basal laminae: 1 by above & 2nd by endothelial cells
- capillary endothelial cells linked by tight junctions
what back up mechanism is in place if antigen gets thru blood-thymus barrier?
macrophages hover nearby
Hassal’s corpuscles
aka thymic corpuscles
round globular mass of ERC cells
function: suggested that they secrete factors that aid thymocyte development
function of fibroblasts in thymus?
external framework only
capsule & trabecule, not part of network
what cell types are found in the thymus?
lymphocytes
epithelial reticular cells
fibroblasts
macrophages
thymic involution
shrinking of thymus with age
replaced by adipose tissue
starts transition during puberty
DiGeorge Syndrome
rare congential disorder
failure of thymus to develop properly
cause: faulty developmement of 3rd & 4th pharyngeal pouches (chromosome 22)
result: poor T cell production→ increased susceptibility to viral, fungal, & bacterial infections
MALT
mucosa-associated lymphatic tissue
diffuse lymphatic tissue
foudn in digestive, repsiratory, & genitounrinary tracts
Peyer’s patches
aggregates lymphatic nodules in teh wall of the ileum
what cells make up a 1º lymphatic follicle?
naive & memory B cells
why does the germinal center of a 2º follicle stain lighter than its cortex or 1º follicle?
proliferation of B cells after antigen presentation & larger B cell size due to antibody production
what is a plasma cell?
a mature B cell that secretes antibodies
larger cytoplasm volume cause them to stain lighter
what is the name of the darker stainging rim of a 2º follicle?
mantle zone
what is the characteristic appearance of folliculra dentritic cells?
multiple long, thin hairlike projections that run between B cells in GC
follicular dendritic cell function
capture & retain antigens for long time (weeks-years)
NOT APCs
of mesenchymal origin
what are dendritic cells derived from?
monocytes
what is the most important/best APC?
dendritic cells
what cells are antigen presenting cells?
dendritic cells
macrophages
B cells
thymic epithelial reticular cells
what are HEVs and where are they found?
high endothelial venules
specialized blood vessels where naive lymphocytes enter 2º lymphoid tissues, except spleen
how do HEVs differ from regular endothelial cells of veins?
they are simple cuboidal/columnar cells instead of squamous
express addressins that atrract T & B cells
lymphocyte homing
adhesion of circulating lymphocytes in blood to cells of HEVs w/in lymphoid organs
circulatory path of lymphocytes
blood→ HEVs→ 2º lymphoid organ→ lymph→ blood
M cells
aka microfold cells
isolate lymphoid nodules from lumina of tract
transfer antigen from lumen to nodule via transcytosis→ NOT APCs
deep invagination of basal surface filled w/dendritic cells & macrophages, B+T cells present further from lumina
immune response generated in lamina propria
present in GI & bronchial MALT
what is the functional importance of the appendix?
filled w/lymphocytes & lymphoid follicles
store normal gut bacteria
what is the ring of waldheyer?
masses of lymphoid tissue that form a ring in posterior mouth
1st line of defenseagainst ingested or inhaled foreign pathogens
palatine tonsils
lateral walls of oral pharynx
dense lymphoid tissue, forms band of lymphatic nodules
non-keratinaized, stratified, squamous epitelium w/multiple invaginations called crypts
partial capsule of dense connective tissue
efferent lymph vessels only
lingual tonsils
@ base of tongue
numerous nodules surrounding single crypt
lined by non-keratinized, stratified, squamous epithelium
thin, partial capsule of dense connective tissue separates from underlying tissue
pharyngeal tonsils
aka adenoids
roof of nasopharynx
nodules w/o crypts
typical respiratory epithelium (pseudostraitified ciliated columnar w/goblet cells)
thin partial capsule of dense connective tissue
lymph
clear fluid that circulates around body tissue
plasma that leaks from capillaries to surround & bathe tissues drains into lymphatic vessels
flows in one direction: to heart
filtered thru lymph nodes along way
what is the size of a lymph node?
pea-grape
what cells are found in the paracortex of a lymph node?
T cells
what cells are found in the medullary cords of lymph nodes?
plasma cells
where are B cells concentrated in lymph nodes?
cortical follicles
flow of lymph thru a lymph node
afferent lymphatic vessel→ subcapsular sinuses→ peritrabecular sinuses→ medullary sinuses→ efferent lymphatic vessels
what substructure are HEVs found?
paracortex
(of lymph nodes, tonsils, Peyer’s patches, appendix)
functions of spleen
remove aged/damaged RBCs from circulation
mount immune response to antigen in circulating blood
structural features of spleen
enclosed by dense connective tissue capsule w/trabeculae
hilum w/neurovasculature
NO afferent lymph vessels
**terminal arterial capillaries
red pulp
75% of spleen mass
where blood is filtered
sinusoids & splenic cords
white pulp
production site of lymphocytes which migrate to red pulp to enter circulation
mostly B cells
what are sheathed capillaries of the spleen sheathed by?
macrophages
PALS
periarteriolar lymphoid sheath
central splenic arteries surrounded by T cells w/nodules of B cells
role of the marginal zone
between PALS & red pulp
trap particulate antigen from circulation & present it to lymphocytes
stave cell
special elongated endothelial cells in spleen
oriented parallel to sinusoid’s blood flow
wrapped in reticular fibers
how much of circulating blood is found in the spleen?
1/3
effects of splenectomy
modest increase of circulating WBCs & platelets
diminished responsiveness to vaccines
**increased susceptibility to infecion by bacteria & protozoa
What are the components that make up the pharyngeal arches?
- neural crest cells: a+v+n, skeletal component (cartilage)
- mesenchymal core (will become musculature)
- ectoderm (outside)
- endoderm (inside)
what is a rhombomere?
segmentation of the neural tube in the hindbrain