histology - kidney, etc Flashcards
how do systems extrinsic to the kidneys affect the kidneys? if sense BP too low <80~~
sympathetic NS -
SNS - what can it do?
carotid sinus - glossopharyngeal, CN 9
aortic sinus - vagus CN 10
message to brain, 2 messages can be sent -
1 - alpha 1 adrenergic receptors on afferent arterioles to CONTRACT
2 - to JG cells - to stim renin - this on beta 1 adrenergic - increases calcium in JG which stim renin production
What does renin do? What is it? Renin is enzyme
aldosterone (glomerulus cortex adrenal0
Angiotensin II, binds to many receptors in the body to affect several systems. It can increase blood pressure by constricting the blood vessels. It can also trigger thirst or the desire for salt. Angiotensin is responsible for the release of the pituitary gland’s anti-diuretic hormone.
liver producing angiotensinogen (protein) -
w/ Renin becomes angiotensin 1
from lungs ACE
becomes angiotensin II
effects adrenal to make ALDOSTERONE
(which creates absorption of sodium - hence BP up) in distal convoluted tubule
in kidney - vasoconstrictor
hence BP up
prox convulated tubes - brush border
microvilli
tons of mitocondria - REABSORPTION -
pinocytic vessels
Osmosis
exocytosis
microvilli - increases surface area, lateral folding and basal invaginations ALL facilitate reaborption and secretion of substances
microvilla - longer than distal, cuboidal, acidophilic PINK
interdigitations
tight junctions - major reabsorption
folds in lateral surface - plicae and
BASAL BORDER invagations and tons of mitrochondria - active transport - ATP
reabsorption function -
all glucose
amino acids
85% NaCL and Hx0, Po4, Ca++
protein
secretions - creatinine (from muscles)
pinocytosis - active ion trasnport NA+/K ATPase
glomerulus
really capillaries - special kind - blood runs thru, and some goes out and becomes urine or starts to become urine
Aquaporin 1
aquaporin-2 (AQP2), located in collecting ducts (
in proximal convulated tubules - 70% water, bulk of solutes
Aquaporin-1 (AQP1), located in proximal tubules (PT) and descending thin limbs of Henle (DTL), and aquaporin-2 (AQP2), located in collecting ducts (CD), are channels involved in water transport across renal tubule epithelia
cortical portion of collecting tubules?
in inner and outer medulla
disorders of Prox conv tubules? PCT
can’t reabsorb - missing ATP
Fanconi syndrome is a rare disorder of kidney tubule function that results in excess amounts of glucose, bicarbonate, phosphates (phosphorus salts), uric acid, potassium, and certain amino acids being excreted in the urine.
fanconi syndrome - hereditary or acquired - fail to reabsorb because decrease in ATP - can’t use the sodium pump
cystinosis - most common cause in kids
cystinosis?
most common in kids???
when reaborbed thru walls - where go?
blood
loop of henle?
thick descending limb - simple cuboidal epith - structural similar to PCT
thick or thin descending lined w?
simple squamous epith
thick ascending -
simple cuboidal - more like distal convulated tubules DCT
four types of epithelial cells
type 1
not much going on
type 1 -
SHORT LOOP nephon
thin descending and ascending thin, simple epith - almost no interdigitations
few / no organelles
type 2
LONG NEPHRON - lots of organelles
Juxtamedullary nephon for types 2,3 and 4
thin descending LONG LOOP many small, blunt microvilli - organelles,
lateral interdig varies on species
cortical labyrinth, taller epithelium -
type 3
inner MEDULLA
thin descending INNER MEDULA, thinner epith, fewer microvilli,
lateral interdigitations absent
type 4
at bend of Loop
and entire thin ascending - flattened epith w/o microvilli, few organelles
type 4
at bend of Loop and up to THICK
and entire thin ascending - flattened epith w/o microvilli, few organelles
function loop henle?
reabsorb !! 15% of filtered water and 25% filters NACl, K+, Ca2+, HCO3-
where urine formed - hypertonic urine, water retention
thin descending p permeable to water
ascending - impermeable to water, but permeable to NA+, K+, CL-
distal convoluted Tubule CVT
Vascular pole
location - continuation of thick ascending, goes back into CORTEX - vascular pole of renal corpuscle - juxtaglmerular region
-
here find?
Macula Densa
DCT?
no brush border
Do have tons of mitochondria
simple cuboidal, smaller thatn PCT, lack brush border, few Microvilli, basal infolding are present with mitochondria
function of DCT
Aldosterone affects here - to reabsorb sodium and water
influence of aldosterone
absorb NA and Hx0
secrete K+
reabsorb bicarb ion and secretion of H+
converts ammonia to amonium
Addison disease? SALTY URINE
aldosterone deficiency - excessive loss of sodium in urine
PCTS vs DCTS
both reabsorb
adjacent to renal corpuscles
PCTs lysosomes - stain dark
DCTS - lightly stained?? which is pink?
apical domail of PCT has brush border and vesicles - DCT fewer of both
both TONS of mitrochondria
tight junctions
collecting tubules and ducts - empty into minor calyx
in cortex - seem tubules and ducts
tubules to duct
cuboidal to columnar - varies from squamous to columnar
weakly staining
few organelle
no basal striations
clear intercellular borders,
empty in to minor calyx at renal papilla
medullary collecting ducts - no tubules in medulla
(lower down) cuboidal cells and change to columnar
COLLECTING DUCTS -
two types of cells?
antidiuretic hormone (Light cells) - ONE CILIUM - reabsorb sodium and water and release Potassium - they have antidiuretic (antipee) hormone ADH - Aquaporin 2
antidiuretic is VASOPRESSIN
light vs dark cells
DARK - intercalated -
principal or light
dark or intercalated
principal single cilium, few short microvilli - small mitochondria - contain antidiuertic hormone ADH water channels AQUAPORIN 2 water channel
dark cells - small, many mito - microvilla on apilca - no basal ifolding - decrease as duct approach papilla
dark cells vs light
fewer mito in light cells
Aquaporin-1 (AQP1), located in proximal tubules (PT) and descending thin limbs of Henle (DTL), and aquaporin-2 (AQP2), located in collecting ducts (CD), are channels involved in water transport across renal tubule epithelia.
secrete H+ and reabosrob K_
light cells - reabosorb NA and water and secrte K_ - primary cilium
aldosterone -
secreted from adrenal gland cortex
angiotensin 2
stim aldosterone secretion - stim epith distal convulated tubules - to reabsorb sodium -
hypothalmus involved to??
??
water channels in ?
principal or light cells
disorders -
polycystic kidney disease
polycystin 1 - membrane receptor -
cell to cell adhesion molecules
extensive cystic enlargement of both kidneys cysts from dilation of collecting tubules - hypertension, renal failure
mutation PKD1 and 2 - predominantly in cilium lining collecting tubules
PKD1 gene account for 85-90% of cases
polycystin 1 is calcium permeable channel
complete loss (need to finish notes)
once form cysts - block
blood flow, hypertension, renal failure
kidney enlarges, tons of cysts - can’t function normally
fuction of tubules and ducts
ADH vasopressin -
causes epithelium to be permeable to H2o
reabsorb H20 and aldosterone
medullary rays?
where see tubules, collecitng ducts in medulla - heading toward renal papilla, minor major calyxes, renal pelvis
diuretics -
promotes the increased production of urine.
stopping reaborb sodium, water
drugs increase output of urine - act
osmotic diuretics
inhibit reabsorb of water and solutes in PCT
thiazide diuretcs
inhibi reaborb NAcl in DCT
carbonic anhydrase
block CA on luminal membrane in PCT
loop diuretics - furosemide, etc
inhibits na_/K+/2cl cotransportor on luminal membrane of thick ascending limb of loop of Henle
carbonic anhydrase
in PCT
decrease hydrogen formation in lumen - hence less sodium reaborbed, but becomes urine
block CA on luminal membrane in PCT
Thiazides - distal tubules - inhibit NAcl cotrasnporter
increase urine w/ na_ and CL
potatssium sparing various
aldosterone receptor antagonist
AMILORIDE and TRIAMTERENE - direct block of sodium Na_ channel blockers
Interstitial cells?
what fills in space - between all ducts -
maintenance of renal architecture and production of
erythropoetic EPOS
in renal cortex and medullary fibroblasts
EPO - producing fibroblasts - stimulator to make RBCs major growth factor for RBCs
blood oscygen down? RBCS made EPO fires it up
renal medullary fibroblast - like cells
contain actin - may secrete prostaglandins and may regulate papillary blood flow
participate in interstitial pephritis - tubulo ?? disease
excretory pathway
UROTHELIUM
minor, major calyces, renal peliv ureters, urinary bladder, urethra
mucosa - trasntional epith - and called
ureter
mucosa, foldeed, start shape - trasntional epithelium, lamina propriate (dense fibro CT)
muscularis - inner longitudinal, outer circulat
in terminal portion of ureter - thcih outer longitudinal muscle is present
adventitia
urinary bladder
mucosa - lined with transitional eptih, lamina propria
muscularis DETRUSOR - fibers in all directions, innter and out long middle circular, forms INTERNAL URETHRAL SPHINCter near opening of urethra
adventitiaaioa - mesothelium
transitional epith
can expand without losing coitinuity -
dome shaped cells
thicker when ?
male urethra
three parts - prostatic
ejac ducts and ducts of proetrate gland penetrate wall - trans. epith
membraneous
strat columnar or speudostratified
penile
- corpus spongiosum, cavernous tissue
pseudo stratified to stratified squamous
ducts of bulbourethral glands - cowpers
secrete mucous
female urethra
shorter - longitudinal folds
trans epith change to strati squa at mid portion
urethal glands, pair or parurethral glands into lomen
lamina propria highly vasculariezes
distally striated muscle form external urethral sphinchter
adventitia - outer covering of fibroelastic CT
3 layers of testis?
tunica vaginalis - single layer on basal laminal - simple squamous
t. abugenia - thick dense fibroelastic CT, coll fibers, fibroblasts, mast cells, smmoth mus, nerve, Messner nerve endings
t. vasculosa - blood vessels in loose CT
testis capsule
can contract periodically
maintains correct pressure
regulated fluids in and out
massages duct system- aid moving sperm
tunica albuginea - posterior surface divides and forms?
mediastinum testis - 250 pyramidal compartments - TEST. LOBULES
incomplete - and can communicate betw lobules
what do testic. lobules have?
1 - 4 seminiferous tubuules - in loose CT rich with blood, lymph, nerve, and LEYDIG “interstitial” cells
mesothelial cells?
tunica vaginalis cells
Mesothelial cells form a monolayer of specialised pavement-like cells that line the body’s serous cavities and internal organs. The primary function of this layer, termed the mesothelium, is to provide a slippery, non-adhesive and protective surface.
Leydig cells, also known as interstitial cells of Leydig,
are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH)
What do Leydig cells do?
produce testosterone in the presense of LH
Where does LH come from?
anterior pituitary
where does FSH come from?
anterior pituitary
Gonadotropic cells
are endocrine cells in the anterior pituitary that produce the gonadotropins, such as the follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Release of FSH and LH by gonadotropes is regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus.
What cells in hypothalmus release GnRH?
preoptic nucleus - oxytocin?
arcuate nucleus
Androgen?
The predominant and most active androgen is testosterone, which is produced by the male testes. The other androgens, which support the functions of testosterone, are produced mainly by the adrenal cortex—the outer portion of the adrenal glands—and only in relatively small quantities.
what secretes androgens
Testicular androgen secretion is controlled by luteinizing hormone (LH) and follicle stimulating hormone (FSH), which influence the Leydig cell response to the LH. … Inhibin production of the Sertoli cell is stimulated by androgens.
Inhibin secreted by Sertoli
tells hypothalmus and pituitary there is enough SPERM - negative feedback loop
what do Sertoli cells do?
blood testis barrier
nourish sperm
create inhibin
1st year only
The supporting cells (Sertoli) are located within the seminiferous tubules. Their task is the creation of a hemato-testicular barrier and the nourishment of the spermatozoa. They can only proliferate in the first year of life (their equivalent in the woman are the follicular cells).
What types of hormones does the adrenal cortex secrete?
Secreted Steroids
Five classes of steroid hormones are produced in the adrenal cortex: glucocorticoids, mineralocorticoids, progestins, androgens, and estrogens.
What stimulates Sertoli cells?
FSH - which creates Androgen binding protein ADP- which combines with testosterone to keep testosterone fluid and around
In addition to stimulating spermatogenesis, FSH also causes the Sertoli cells to produce an androgen binding protein (ABP). This protein binds testosterone and helps maintain a high concentration of testosterone within the testes; this is essential for spermatogenesis to occur.
Is testosterone a testicular androgen?
yes -
rete testis?
A network of small tubes in the testicle that helps move sperm cells from the testicle to the epididymis. The epididymis is where the sperm mature and are stored.
seminiferous tubules?
highly convoluted, but at apex of lobule becomes a STRAIGHT tubule
layer of fibro connective tissue (tunica propria) - 3 - 5 layers of fibroblasts, and one layer of muscle - flattened myoid cells
complex of germinal or seminiferous epithelium - two types
SERTOLI cells
Sperm germ cells (spermatogenic lineage cells
in the interstitial spaces are the LEYDIG cells
spermatogenic lineage cells
stacked in 4 - 8 layers that occupy space betw basal lamina and lumen
spermatogenesis - how many phases?
3 -
mitosis - A cell is daughter cells - doesn’t leave Basal compartment
meoisis 1 and meoisis 2
spermatogonia divide to create primary spermatocytes, 2dary spermatocytes, spermatids , spermatozoa
division of seminiferous tubules?
basal compartment, adlumen compartment, lumen -
blood testis barrier between basal and adlumen - via tight junctions between sertoli cells
what’s a spermatogonium?
primitive germ cells in basal compartment - will divide via mitosis two create 2 identical cells - one cell will remain in basal compartment and renew the cycle -
each contains a diploid number of chromosomes
What happens at male puberty?
spermatogenesis begins -
spermatogium types
A dark, A pale, B?
A dark, A pale, B
A dark - renew themselves and create some A pale - ovoid nucleus - stain dark
A PALE - ovoid nucleus - divide mitotically to create more A Pale and some B
B - spherical nucleus, dense stain, divide via mitosis to create PRIMARY spermatacytes
Primary spermatocytes
largest germ cell in tubule -
start in basal compartment - but after division migrate to middle zone -
spherical or ovid, nucleus in some stage of karyokinesis (division of a cell nucleus during mitosis.)
soon after - become secondary spermatocytes
Quick change - what cells are hard to see?
secondary spermatocytes - they divide quickly into spermatids
spermatids -
small size - nuclei w/ condesnesed chromatin, juxtaluminal location with tubule
spermatid - complex process
- form acrosome
- condense, elongate nucleus
- develop flagellum
- loss of much of cytoplasm (becomes sleek and excited to move!)
When mature released into lumen of seminif tubule
4 phases of spermiogenesis
- GOLGI phase,
- cap phase
- Acrosome phase
- Maturation Phase
- golgi phase - PAS positive proacrosomal granules accumulate in Golgi - fuse to form single granule in a membrane ACROSOMAL Vesicle
CENTRIOLES migrate near surface and opposite to forming acrosome
- cap phase - ACROSOMAL reaction when find an ova
vesicle and granule cover anterior half of condensiing nucleus - “cap”
within has several hydrolytic enzymes - hyaluronidase, neuraminidase, acid phosphatase, acrosin - wthich dissociate cells of corona radiata and digest zonna pellucida
when spermatozoa encounter ova - the outer membrane of acrosome fueses with plasma membrane at multiple sites known as ACROSOMAL reaction
- acrosome phase
anterior pole of cell (w/ acrosome) orients toward base of seminiferous tubule
nucleus elongates - microtubules may help (the manchettes)
mitocondria aggregate around proximal part of flagellum MIDDLE PIECE
- maturation phase
residual cytoplams is she and phagocytized by Sertoli cells - spermatozoa released into lumne
(during division of spermatonia - resulting cells do not separate completely but remian attache d by cytoplamic bridges
spermatazoa ?
head, middle piece (w/ mitrochondrial sheath) responsible for movement fof tail
tail - covered by thin layer of cytoplas except at tip
Immotile cilia syndrome
infertility - due to lack of dynein or other proteins required for ciliary motility
sertoli cells
on basement membrane - few in number - at intervals between spermatogonia
columnar - extends from basal lamina to lumen - along the side of each cell - a stream of proliferating and differentiating germ cells move slowly toward the lumen
Sertoli cells connected to one another via?
via gap junctions and multiple tight junctions -
tight junctions are near base of cell - separating early vs later developoing sperm - early ones need to have access to hormones from blood
blood testis barrier
all the spermatocyctes, spermatids and spermatozoa are near the lumen - with the thigh junctions creating a blood testis barrier - to protect the spermatogenic cells from noxious substances
the barrier disappears and reappears letting the primary spermatocytes out - and keeping the germ cells (spermatogonia) in the basal compartment
Sertoli functions?
- help and nourish sperm
- phagocytose residual bodies from spermatids,
- secrete fluid into lumen for sperm movement - - including ADP, activin, inhibin, plasminogen activator, transferrin, growth factors, ions
- small quantities of estrogen - (conversion of testosterone to estradiol)
- maybe in embryo - non-sterioidal Mullerian Inhibitory Factor
- prepubertal state - substance suppressing meiotic division of gamets
- Sertoli cells do not divide during reproductive period - extememtly resistant to adverse conditions such as infection, malnutrition or X ray
Interstitial tissue - between tubules?
loose CT, nerves, blood and lymph
fibroblasts, undifferentiated connective cells, mast cells, macrophases
LEYDIG
Leydig?
crystals of REINKE
during puberty - LEYDIG become apparent - cental nucleus - have characteristics of steroid secreting cells - (smoother ER), and crystals of REINKE
leydig produce?
testosterone
leydig stim by?
ICSH (like LH) and Prolactin
ICSH - same as LH in females = from anterior pituitary -
PROLACTIN also aid in production of teststerone
puberty vs. fetal life and testosterone?
lots of Leydig during puberty
fetus - Chorionic gonadotropin from placenta stims interstitial cells of testis to produce testosterone - developing males genitalia
testosterone responsible for?
and male libido
many things - growth, devel, maintenance of accessory male sex organs, prostate, seminal vesicles, bulbourethral glands, penis
and secondary sec changth - hair - larynx enlargment, musculoskeletal growth
crystals of reinke?
Reinke crystals are rod-like cytoplasmic inclusions which can be found in Leydig cells of the testes. Occurring only in adult humans and wild bush rats, their function is unknown.
protein inclusions in cytoplams of leydig
StAR protein regs?
synthesis of steriods by transporting cholesterol across outer mitochondrial membrane - mutation of this is seen in people with defective synthesis of adrenal and gonadal steriods
steroid producing cells?
lipid droplets containing esterfied cholesterol, smooth ER, mitochondria with tubular critae
prolactin?
induces expression of LH receptor
FSH, LH, Prolactin
FSH, and LH by basophils in adenohypophysis of pituitary
PROlactin- by acidophils
fsh bind to?
sertoli which produce ABP, which binds to testosterone - and complex is transported to epididymis
Prolactin stims leydig to express LH receptors = LH binds triggering testosertone production
testosterone - 3 secretory routes?
blood circulation
lymphatic channels surroudning seminif tubules
sertoli cells where binds to androgen receptor
feeback loops - 2 regulating spermatogeneiss?
FSH and LH
GnRH in hypothalamus modulated FSH inhibi-activin loop
LH - testosterone loop
1 sertoli = inhibit if too many sperm
ACTIVIN when want more (up-regulate FSH secretion)
2LH - testosterone loop
temp for testis important
BELOW 37 - about 35
rich venous plexus helps with counter current exchange -
failure of descent - - inhibits - too warm
malnutrition, alcoholism and some drugs alter spematonoia production
primordial germ cells come from?
yolk sac endoderm
urinary and genital systems develop from what mesoderm?
Kindermediate
skelton arms, legs - dancing on PLATE
intermediate - kidneys and gonads
lateral plate - appendecular skeleton -
paraxial condenses to form somites - giving rise to axial skeleton, voluntary muscles, and dermis
What cell secrete in the fetus secrete glycoprotein hormone - determining male sex?
SERTOLI
sertoli -
SRY gene on Y chromo - testis determining factor -TDF _ females develop in the absense of SRY - under influence of TEF SErtoli differentiate in primitive sex cords and secrete MIF (mullerian inhib factor) secrete until puberty
principle affect of testic determining factor on devel of male reprod system?
organizaiton and differntiation of gonadal cords
during 5th week - indifferent gonads form finger like cords - in males - TDF ecoded by SRY gene stimulates primitive sex cords to extend deeper into medulla of gonad - TDF stims differntitiona of Sertoli and Leydig cells - which secrete mullerian inhib factor and testosterone respectively.
testosterone regs devel of male genitalia and differentiation of mesonephric tubes and ducts -
regressions and loss of uterus and uterine tubes are regulated by mullerian inhib factor
TDF belongs to which family of proteins?
nuclear transcription factor
most common surgical treatment for infants?
failure of testis to descend - often do with first year
which testicular cells see a lot of under microscope?
primary spermatocytes 1 - 22 days arrested - allowing for crossover affect - - secondary short lived cells =
recognize a sertoli cell on microscope?
columar - attaced to basal membrane - apical faces lumen
leydig tumor in male child?
can create precocious phys/sexual development
synthesizing steroids?
Smooth ER - and lipid droplets (foamy apperaance) (same with foam cells in adrenal cortex)
intercellular bridges?
help regulate germ cell diffentiation by ensuring free diffusion of singaling moecules, FNA, and proteins between daughter spermatocytes and spermtids
daughter cells from single Type A dark stem cell - remian connected to one another thru these - they share resources - lost prior to release of spermatozoa in to lumen
what found in middle piece of spermatozoa?
mitocondria
assembly of microtubules in sperm?
neck of sperm contains pair of centrioles tha organie the 9+2 arramengemnt of microtubules in flagellum
centrosomes initiate the assembly
(centromere - region of DNA organizing and linking sister chromatids together)
CentroMIRROR
hyperactivation of sperm motility ?
opening of membrane ca2+ channels
age related thickening of tunica propria in testis?
infertility - delivering nutrients and oxygen to sperm germ cells comes thru peritubular fascia (tunica propria)
what do late spermatids do?
break their bridges and get rid of excess cytoplasm - generating residual bodies for phagocytosis - after this SERTOLI cells release them into the lumen and phagocotyse resid bodies
What helps develop male repro system, including growth of genital ducts, and epididymis and vas defense
leydig cells - testosterone!
are Sertoli cells exocrine or endocrine?
Both - release inhibin (fsh) secrete fluid, protein into lumen - ABP to maintain high concentration of testosterone in area -
tunia albuginea?
when sperm enter rete testis - not motile -
when leave epididimus - they are motile
seminif surrounded by thick white coat - w/ septa 250 lobules - each lobule 1 - 4 seminif tubules surrounded by interstitial CT (leydig, etc)
rete testis?
single CILIUM - simple cuboidal - microvilli and single CILIUM
seminif end as short stubs - emptying into interconnected labyrinth of channels - in midiastium of testis continguous with tunica albugenia
efferent ductules of testis?
scalloped appearance re two types of cells
psesdostratified epith
principle cells with microvilli &
ciliated cells beat sperm toward epididimus
cilia - transporting sperm from rete testis to caput epididymis - two groups of cells - tall with cilia to move sperm, other cuboidal w/ microvilli for water absorption
lining of epididymis and structure 2 cells
principal cells with stereocilia
basal cells
sterocilia have neither basal bodies nor microtubules whereas cilia has both
lined with steriocilia (not actual cilia) - non-motile
epidid - has three structures - caput, corpus, cauda = during movment thru here sperm become mature, with capitaciation and fertilization capacity
end of epididymal duct - sperm has motility
epidydmus - sperm maturation - 2 - 12 days - aquire motility and fertilizaton capapcty i from body to tail
vas deferens? - thick muscle
has mucous membrane, very thick muscular coat and fibrous coat - adventitia
from posterio wall of testis, thru inguinal canal - entering abdomen to join protate - when enters prostate becomes “ejaculatory duct” -
THICK muscular wall - to move sperm along - three layers of muscle - inner long, middle circ, outer longi - to expel sperm during ejaculation-
Thicker wall than any other part of male genitalia
excurrent genital males genitalia develop from?
mesonephrnic ducts 4 - 8 wks - interim kidney
paramesonephric duct forms uterus and uterine tubes -
ureteric diverticulum gives rise to ureter, renal pelvis, major, minor calyces, collecting tubules/ducts of per. kidney (a branch of mesnephric duct)
embryonic development of urorectal septum?
grows and divides the primitive hindgut (cloaca) into urogenital sinus and rectus - primiative hindgut lined by endoderm. urogenital sinus divided into three parts - carnial (vesicle forms bladder) middle (pelvis) forms urethra) and prostate in males, urethra in females - and caudal pahllic part grows genital tubercle to form penis/clit
is prostate from ectoderm or endoderm?
endoderm
dartos fascia?
regs temp - wrinkling scrotum
superficila fascia of scrotom and penis
The dartos muscle is the scrotal part of the dartos fascia, composed by smooth cells. In the scrotum, the tunica dartos acts to regulate the temperature of the testicles, which promotes spermatogenesis. It does this by expanding or contracting to wrinkle the scrotal skin.
The seminal vesicles - 70% of fluid contribution - much fructose
(also called vesicular glands, or seminal glands), are a pair of two coiled tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen.
tortuous tubes - surrounded by muscle
prostate ?
periferal - most cancer - on outside
trasntional - older men - can’t pee compress benign nodules
3 zones -
central, transitional, peripheral
central surrounds ejac ducts -
transitional around prostatic urethra
enlargement of prostrate can affect these structures - retaining urine and predisposiing to recurrent urinary track infections -
nodular hyperplasis is common disorder - enlargmenet of gland - obstruction to flow of urine
corpora amylacea?
w/ no clinical significance
secretory material of prostate
small hyaline masses found in the prostate gland, nervous system, lung, and sometimes in other organs of the body.-
penis?
paired corpora cavernosa - w/ ventral corpus spongiosum
tunica albugieum surrounds it all and hold cylindrical erectile masses togetehr
tunica vascularis and tunica vaginalis are investiing layers of testes
what does corpus spongiusum eventually form
glans penis
what arteries supply penis?
internal pudendal
erectile function?
Nitrous Oxide
dilation of helicine arteries - parasympathetic relax trabecular smooth muscles surrounding these arteries -
young male tumors on testis?
primordial germ cell tumors - usually benign - become activated to initiate embryonic develoepement - have all three germ layers - ecto, meso, and endo derm
which testis larger?
commonly right
testis contain?
seminif tubules, straight tubutes, rete testis, leydig (interstitial cells) and Sertoli
spermiogenesis?
when spermatids develop into spermatazoa - sleek swimmers = spermatids are round!
PSA from prostate?
if find in blood - maybe a disease
liquifies semen after ejaculation
seminal vesicle?
70% volume - fructose -
kidney cont’d
cleans the system up - saves what they can - gets rid of what they don’t need thru urine
figures out what the system needs - and can signal other parts of system to make more of something
excretes poisons, extra things not needs,
can do gluconeogenesis - starving - can release glucose
secrete EPO - tells blood marrow to make RBC
secretes renin
vitamin d function- signals osteoblasts to secrete IL1 - which messages osteoblasts to increase bone resoprtion
collecting ducts and major/minor calyces comes from what fetal structure?
ureteric bud
kidney during fetal life most imp role?
generate amniotic fluid - produce urine
what surrounds kidney?
dense CT capsule - - outer layer and inner layer of myofibroblasts - can contract!
renal lobule?
multiple nephrons draining to single collecting duct
renal arteries?
SEGMENTAl - no segmental veins
branch to form two or three segmental arteries that enter each kidney at hilum - interlobar arteries are branches of teh segmental renal artieers that travel betwe renal pyramids - - extend toward corticomedullary junction - where give rise to arcuate arteries - they ARC along corticomedullary junction near baes of renal pyramids -
primary urine
produced in glomerulus - and heads out to be further refined - produced in the “renal corpuscle”
renal corpuscle vs glomerulus
renal corpuscle - two structures -
bowman’s is a complete sac housing a glomerulus
The renal corpuscle is composed of two structures, the glomerulus and the Bowman’s capsule. The glomerulus is a small tuft of capillaries containing two cell types. … Mesangial cells are modified smooth muscle cells that lie between the capillaries.
glomerulus is a small tuft of capillaries containing two cell types.
Endothelial cells, which have large fenestrae, are not covered by diaphragms. Mesangial cells are modified smooth muscle cells that lie between the capillaries.
two poles of renal corpusulce
vascular - afferent, efferent invaginate parietal layer of bowmans
urinary - where PCT begins
cap network in glomerulus?
discontinurous caps with fenestrations lacking diaphragms - fenestrated endothelial cells rest on continuous and thick basement membrane - perforation through these thin cells exists - lacking diaphragms - larger cells can get thru
glomerular basement membrane?
TYPE 4 COLLAGEN
cap endoth cells and visceral epithelia cells (podocytes) syntheis this - made of TYPE 4 collagen, laminein, etc
podocytes - wrap around capillaries and that neighbor cells of the Bowman’s capsule.
viceral layer of bowman’s cap - closly associated with basement membrane - protrude into urinary space -
foot processes of podocytes
are visceral eptih cells resting on outer surface of glomerular basement membrane - sending out extensive foot processes or peicels
slit diaphragms
between foot processes - modified adherens - w/ fenestrated caps and continuous membrane - these structures form a size and charge selective barrier than regulated filtration
nephrin? protein
connects slit diaphramgs - form zipper-like sheets that ineract to form a prous slit diaphram - >3.5 nm can’t pass
Pars nervosa. posterior pituitary -
oxytocin
vasopressin
herring bodies
Also called the neural lobe or posterior lobe, this region constitutes the majority of the posterior pituitary and is the storage site of oxytocin and vasopressin. Sometimes (incorrectly) considered synonymous with the posterior pituitary, the pars nervosa includes Herring bodies and pituicytes.
kidney functions
1. filter, excrete 2, balance fluids 3 recover, reabosorb 4 regulate blood pressure - RENIN 5. EPO - (endocrine function - RBC 6, Vitamin D derivative - 1/25 hydroxy... calcium metab
Renin angiotensin system RAS triggers?
- depletion of fluid (hypovolemia)
- low BP (hypotension)
- Low NA+ at macula densa
afferent arteriole - can it sense pressure?
YES - when BP low - renin secretion is stiumulated
tubuloglomerular feedback?
macula dense links changes in sodium to regulates blood flow - via message to JG cells and mesengial which can ??
need to review slides re angiotensin renin thing
first four slides in his presentation - can print out too
kidney - cortex (outer and justamedullary)
medulla (outer and inner)
capsule - two layers - outer
inner - myofibroblasts -
cortex?
part of nephron except tubules
renal corpuscles - with convoluted and straigh tubules - collecting tubules, collecting ducts, vascular supply
outer medulla -
thick PCT and some thin
inner medulla
thin tubule and distal collecting ducts
medullary rays?
straight tubules and collecting ducts -
vertical striations emananting from medulla can be seen in corte
cortical labyrinthc?
region between medullary rays with renal corpuscles, convoluted tubes and collecting
medulla - straight tubules, collecting ducts and ???
special capillary network VASA RECTA
vasa recta
runs parallel to tubules and is part of countercurrect exchnage
tubules form
pyramids - bases of pyramids face cortex and apices face renal sinus
each pyramid divides into
outer medulla and inner
outer medulla - has OUTER and INNER stripe
renal columns represent cortical tissue contained with in medulla
Lobes and lobules?
medullary pyramid - = renal lob -
lateral boundariy of each lobe - renal columns of BERTIN (residual structures representing fusion of primitive lobes within metanephric bastema
apex of each lobe terminates in conic shaped pappilla - by area crirosa (opening site of papillary duct -
papilla surrounded by minor calyx
minor calyx?
collects urine from pilla dripping from area cribrosa
converge to form major calyces whit head to renal pelvis to ureter
lobule?
portion of cortex flanked by two adjacent ascenting interlobular arteries
each interlobular artery gives rise to series of glomeruli - each constistn of afferenate arteriole, cap nextework and efferent
medullary ray is
axis of lobule
cortex has many lubules and each lobule has a single medullary ray
interlobar arteries
Between the pyramids are major arteries termed the interlobar arteries. Each interlobar artery branches over the base of the pyramid.
interlobular arteries
Cortical radial arteries, formerly known as interlobular arteries, are renal blood vessels given off at right angles from the side of the arcuate arteries looking toward the cortical substance.
describe glomerulus arterial system?
afferent artery - capillary (glomulerus) - efferent - vasa recta (where turns from cap to venous) venule
uriniferous tubules?
1.3 million in each kidney - surrounded by stroma with loose CT, blood vessels, lymph, nerves
each uriniferous tubule consists of?
nephon and collecting duct
nephron - 2 components -
renal corpuscle
long renal tubue - with several regions
ureteric duct embyology gives rise to ?
REVIEW THIS!
The ureteric bud (also known as the metanephrogenic diverticulum) is a protrusion of the mesonephric duct that appears during the embryological development of urogenital organs. It will eventually form the urinary collecting system (i.e. collecting tubes, calyces, renal pelvis, ureter) of the kidney.
nephon and collecting duct - two different embyological systems?
nephron goes all the way to distal convoluted tubule
Mesonephros develops by the formation of mesonephric tubules from the intermediate mesoderm, it is the principal excretory organ during early embryonic life (4—8 weeks). … Metanephros arises caudal to the mesonephros at five weeks of development; it is the permanent and functional kidney in higher vertebrates.
The development of the kidney proceeds through a series of successive phases, each marked by the development of a more advanced kidney: the archinephros, pronephros, mesonephros, and metanephros.[1] The pronephros is the most immature form of kidney, while the metanephros is most developed. The metanephros persists as the definitive adult kidney.
collecting tubules - 3 regions
cortical collecint (in renal cortex as centerpiece of medullary ray)
outer medullary
inner medullary
two types of nephons
cortical or justamedullary
cortical - short loop of henle
juxta - henle loop goes into inner medulla
nephron - renal corpuscle or MALPIGHIAN Corpuscle
bowman’s capsula and glmerulus
bowman’s capsule?
two layers - viscerla (attached to cap of glmerulus)
parietal
visceral lined by epithelial cells called PODOCYTES - on a basal lamina
partietal layer - covered by basal lamina w/ s
simple squamous epith - and is continuous with simple cuboidal epith of proximal convoluted tubule
urinary space - between visceral and parietal
and continguous with Urinary POLE
other pole VASCULAR
3 components of glomerulus
caps, mesangium (in mesangial matris) and pococytes - compoent of visceral layer of capsule of bowman
sympathetic nerve stim to afferent - innervating JG cells?
stim RENIN
JG cells are what type of cell?
modified smooth muscle
where do podocytes bulge?
into urinary space
what cells cover parietal layer of bowman cap?
squamous epithelial
where are macula densa cells found?
thick Distal Convoluted Tubule at affereant artery - in contacct with extraglomerial mesangial cells
5 components of juxtaglomerial apparatus?
afferent efferent macula densa mesangial JG cells
podocytes?
long, branching porcesses that completely encircle surface of glomerular capillary
glomerular filtration system?
fenestraed endothelia cells, basal laminal, podocytes
filtration slits?
gaps between podocytes - bridge by slit DIAPHRAM
what attached pedicels to basal lamina?
INTEGRIN
Nephrin?
makes up filtration slits diaphrgm between podocytes
which is an EXTRA filtering mechanism
what things other than the filtraion barrier limit passage of molecules?
size and charge
Heparin sulfate lines both sides of basal lamina (rara interna, rara externa) has negative charge
what molecules filter best thru?
positive charge, 3.5nm - albumin filters POORLY
what do podocytes secrete?
glomerular endothelial GROWTH FACTOR - stims develop of endothelium and maintenance of fenestrations
endothe is permealbe to ?
water, urea, glucose, small proteins
Basal lamina - what kind of collagen?
type IV - with firbonectin, laminin and heparan sulface
3 parts of filtrations sysmte?
fenestrated endo cell
glomerular basal lamina
filtrations slits between foot processes covered with diaphragm
congenital nephrotic syndrome? Finland - neFrin - problem -
nephrin doesn’t work - albumin slips thru!
podocyte slit filtration diaphragm doesn’t work
ALOT in Finland - see in fetus - lethal
is the glomerular basal lamina fused?
Yes - with endothelial cells and pdocytes -
lamina dense is physical barrier - but lamina rara is a charge barrier
diabetes meelitus and glomerulonephrisit?
glomerular filter is altered - becoming more permeable to proteins - release of protein into urin (proteinuria)
Mesangium?
contraction,
phagocytosis,
CAN PROLIFERATE
secrete prostaglandins and endothlins - (indcue constrictuion of afferent and efferent arterioles
can be intra and extraglomerular
specilized pericytes - smooth muscle characteristics and macrophages -
mesangial cells do a lot -
synthesize matrix and collagen
Mesangial cells and their matrix form the central stalk of the glomerulus and are part of a functional unit interacting closely with endothelial cells and podocytes. Alterations in one cell type can produce changes in the others
indirectly - mechanical support
turnover of basal lamina via phagocytosis
regulate blood flow via contraction
secrete prostalandins and endothelin
respond to angiotensin II
Mesangial cells are specialised cells in the kidney that make up the mesangium of the glomerulus. Together with the mesangial matrix, they form the vascular pole of the renal corpuscle. The mesangial cell population accounts for approximately 30-40% of the total cells in the glomerulus.
Endothelins?
induce constriction of afferent and efferent glomerular anterioles
diffuse mesengial sclerosis?
mesangial cells produce matrix which contains fibronectin and collagens - in some disease - mesantial matric acculutes… obliteration capillaries
mesangial can release cytokinses?
inducing inflammatory reaction leading to occlusion of cap lumen
angiotensin (( and mesangial?
induces contraction
mesangial and phagocytosis?
have ACTIN too
any trapped material coming thru barriers - they can clear out
damage to glomerulus? diseases?
immune mechanism can damage - against cells and basal lamina - glmerulonephritis
antibody-antigen complexes can get trapped in filtration sysytem
autoantibodies can target type 4 collagen
immune complexes can deposit between endo cells and basal lamina, etc
immune complexes in basement membrane (from bacterial, viral, etc infection
triggers proliferatino of endothelial and mesangial cells - neutrophils accumulate in lumen of caps - becoming occluded
This is GOOD PASTURE”S Syndrome
and sytemic lupis -
generally considered type II hypersensitivity reaction.
rapidly progressive glomerulonephritis - immune mediated process -
proliferation of epithelial cells and infiltration of macrophages produce crescent like mass - compressing glmerular caps - which are displaced and stop functioning - RENAL FAILURE
accumulation of fibrin, etcc stim prolifeative process
JG cells produce renin
JG apparatus?
it is a small endocrine structure -
consists of macula densa -
extraglmerular mesantial cells
renin producing cells of afferent art and some efferent
macula dense is sensitive to changes in ?
sodium concentration - renin secretes when SO or BP falls
When is renin released?
when SO or BP falls
tubuloglomerular feedback mechanisms?
JG apparatus
and sympathetic (adrenergic) fibers innervating JG cells
renin secretion enhanced by NE and dopamine secreted by adrenergc nerve fibers
NE binds to B1 cepetors in afferent glomerular arterioles -
NO parasym innervation
Macula Densa of DCT?
cells columnar, able to sense flow and ionic conc
influences afferent arteriole constriction, filtration and renin secretion
JG cells
modified smoother muscle
secretory granules
protein synthesizing organells
synthesize renin
effect - increase NA+ and CL- absorption - distal tubules
Polkissen or Lasic Cells?
Extraglomerular mesangial cells
Blood supply to kidneys?
Renal architeture is TERMINAL - no anastomoses between interlobular arteries
via renal artery
to interlobar arteries running across medulla through renal columns along sides of pyramids
at corticomedullary junction
give off branhes at right angles - ARCUATE arteries
NO anastomose between interlobular arteries
Renal infact can be caused by atherosclerotic plaques in renal artery
interlobular arteries are found?
in the cortex - ascend toward outer cortex, branch sevearl times to form afferent glomerular arterioles
they then form cap network - enveloped by two layers capsule of bowman and continue as efferent
location of renal corpuscle detemines?
peritubular caps - with convoluted tubules
vasa recta - w/ nephron tube
???? he says MOST IMPORTANT FOR YOU TO KNOW - I don’t understand the real difference?
efferent arterior forms two diff cap networks -
peritubular - surrounding superficial cortical sements of uriniferous tubules
drains into interlobular vein - converging to arcuate vein, drain to interlobar veins continuous with renal vein
vasa recta (straight esel) formed by efferent arterioles - located close to corticomedullary junction
extend into medulla - parallel to medullary segment - make hairpin turn reutnr to junction as ascenging venous caps - lined by fenestrated endothelial cells
location of renal corpuscle detemines?
peritubular caps - with convoluted tubules
vasa recta - w/ nephron tube
The vasa recta capillaries are long, hairpin-shaped blood vessels that run parallel to the loops of Henle. The hairpin turns slow the rate of blood flow, which helps maintain the osmotic gradient required for water reabsorption.
efferent arterioles forms two diff cap networks -
peritubular - surrounding superficial cortical segments of uriniferous tubules
drains into interlobular vein - converging to arcuate vein, drain to interlobar veins continuous with renal vein
vasa recta (straight vessel) formed by efferent arterioles - located close to corticomedullary junction
extend into medulla - parallel to medullary segment - make hairpin turn reutnr to junction as ascenging venous caps - lined by fenestrated endothelial cells
peritubular capillaries
critical for reabsorption in CORTEX
are tiny blood vessels, supplied by the efferent arteriole, that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.
The vasa recta
Peritubular capillaries surround the cortical parts of the proximal and distal tubules, while the vasa recta go into the medulla to approach the loop of Henle.
are the straight arterioles, and the straight venules of the kidney, – a series of blood vessels in the blood supply of the kidney that enter the medulla as the straight arterioles, and leave the medulla to ascend to the cortex as the straight venules.
where are vasa recta found?
in MEDULLA
blood flow in kidneys?
afferent, glomerular, efferent
two paths
peritubular (cortex)
vasa recta - medulla - supplying juxtaglo nephrons (only ones that go into medulla) and these loop around in a big long semicrircle
prox convoluted tubules
brush border - microvilli
tight junctions and zonula adherens BELT
begin at urinary pole - simple cuboidal
longer than DCT
acidophillic -
plicae or foldes on lateral surface
PCT functions
AQUAsporin 1 - 70% water reabsorb
Brings sodium in and pumps h+ out
mitocondria are basally located
pinocytosis -
active ion transport (NA+/K+ -ATPase)
osmosis
exoocytosis
reabsorption
secretion
Fanconi syndrome -
hereditary (primary) or acquired (secondary)
cystinosis is most common cause of Fanconi in children
PCT fail to reabsorb amino acids and glucose -
they are secreted in urine
loop of henle
thick - simple cuboidal
thin descending - simple squa, few microvilli
thin ascending simple squa
few microvilli
thicken ascending
simple cuboidal similar to DCT
4 types of epithelial cells
thru tubes -
in LONG looped nephrons - in the cortical labyrinth - taller epithelium - abudant organells, many microvilli
loop of henle
capable of forming hyperonic urine - (water retention)
thin descending [ permeable to water
ascending impermeable to water - permeable to NA+, K+, Cl_
reabsorbs about 15% watera dnd 25% other things
DCT
Aldosterone deficient?
ADDISONS SALTY urine
no brush border - simple cuboidal
under aldosterone influence - absorb na_ and water - secrete K+
deficieny - ADDISONS
cells lining both PCT and DCTs have ?
mitrocondria
diff between PCT and DCT ?
microvilli - and lots of vesicles - in the PCT - lysosomes too -
DCT some microvilli = not a lot
collecting tubes?
empty into minor calyx at renal papilla
few organelles
two types of cells in collecting tubules and ducts
principal or LIGHT cells - pale stain - single CILIUM - few microvilla, small mitocondria, contain ADH - Aguaporin 2 ABSORBING WATER,
DARK or intercalated -
lots of mitocondria no. decrease as duct approach papilla-
two types of cells in collecting tubules and ducts
The principal cell mediates the collecting duct’s influence on sodium and potassium balance via sodium channels and potassium channels located on the cell’s apical membrane. Aldosterone determines expression of sodium channels (especially the ENaC).
he principal cell is one of two major epithelial cell types in what is often referred to as the aldosterone-sensitive distal nephron, comprising the connecting segment through the collecting duct
principal or LIGHT cells - pale stain - single CILIUM - few microvilla, small mitocondria, contain ADH - Aguaporin 2
DARK or intercalated -
lots of mitocondria no. decrease as duct approach papilla-
Principal cells are the main Na+ reabsorbing cells and the site of action of aldosterone, K+-sparing diuretics, and spironolactone. Type A and B intercalated cells make up the second cell type in the collecting duct epithelium. Type A intercalated cells mediate acid secretion and bicarbonate reabsorption.
collecting tube, ducts function?
ADH
ADH - vasopressin - causes epithelium to be permeable to h2O - reabsop of H20
vasopressin, is a small peptide hormone which regulates the body’s retention of water. It is one of only two hormones secreted by the posterior pituitary gland.
diuretics - various meds
osmotic affect PCT and descending thin limb
inhibit water reabsorption or Sodium (loop) - loop diur. affects - thick ascending limb
Interstitial cells in kidney - 2 kinds
maintain architecture and produce EPO -
activated interstitial fibroblast and inflamm cells (macrophages and lymphocytes) participated in nephritis disease -
urinary bladder - mucosa
transitional epith - lamina propria
DETRUSSOR muscle - fibers in all directions - forms internal urethral sphincter
adventitia - loose CT - superior surface covered by mesothelium
Transitional epith
has plaques on plasma membrane - thicker - folds inward when non-distended - form fusiform vesicles
male urethra - three parts
prostatic (trans. epith) - ejac ducts and ducts of prostate gland penetrate wall
membranous - surround to skeletal mus of urogential diaph - to form external voluntary urethral sphicter
penile urethra - surroun tby corpus spongiosum, cavernous tissue - at distal end changes to strat squamous -
ducts of bulbourethral glands (cowpers) and mucus secreteing urtehal gland (of Littre) empty into penile uretha
female uretha
short
longit folkds
lined by trasntional changeing to strat squa -
urethral glands - inner longit outer cirular smooth muscle
external striated muscle
mammary - fat/iga and PINCHED off via aPocrine secreteion
Milk proteins and lactose - MEROCRINE exocytosis
what are integrins and cadherins
cadherins and selectins depend on Ca2+.
Integrins don’t ECM
cadherins between Cells
Cell adherin
CADhein
integrins - btw cell and ECM
Integrins and the Ig-superfamily CAMs do not depend on Ca2+ while cadherins and selectins depend on Ca2+. In addition, integrins participate in cell–matrix interactions, while other CAM families participate in cell–cell interactions.
role of sterocilia in epididymous - non-motile - absorption creates current moving immobile sperm
resorb 90% of this fluid as the spermatozoa start to become motile. This absorption creates a fluid current
The stereocilia in the epididymis are non-motile. … The core function of the stereocilia is to resorb 90% of this fluid as the spermatozoa start to become motile. This absorption creates a fluid current that moves the immobile sperm from the seminiferous tubules to the epididymis.
adrenal layer secretions? ACS
aldosterone
cortisol
Sex hormones 17
mineralocorticoids, glucocorticoids, and androgens
The zona reticularis is the site of biosynthesis of androgen precursors such as dehydroepiandrosterone (DHEA) and androstenedione from cholesterol. These androgens are released into the bloodstream and transported to gonads where they are converted into testosterone or oestrogen.
Zona glomularios – mineral aldosterone
Fasciulta ? CORTISOL
Retincularis SEX – androgens – go to gonads
Cortisol, the primary stress hormone, increases sugars (glucose) in the bloodstream, enhances your brain’s use of glucose and increases the availability of substances that repair tissues. Cortisol also curbs functions that would be nonessential or detrimental in a fight-or-flight situation.
melanocytes produce melanin - which is transported to keratinocytes
Tyrosinase (TANGERINE) is required for melanocytes to produce melanin from the amino acid tyrosine.
What is the function of thyroglobulin?
Thyroglobulin is the other major component needed for synthesis of thyroxine and triiodothyronine. Thyroglobulin is the matrix for thyroid hormone synthesis and is the form in which hormone is stored in the gland
What do parathyroid cells secrete?
oxyphil cells? appear at the onset of puberty, but have no known function.
The parathyroid gland contains two cell types, chief cells and oxyphil cells. Chief cells are the predominant cell type characterised by round nucleus surrounded by scarce cytoplasm. They produce and secrete PTH in response to low extracellular calcium levels detected by receptors in the cell membrane.
Herring bodies - posterior pituitary
or neurosecretory bodies are structures found in the posterior pituitary. They represent the terminal end of the axons from the hypothalamus, and hormones are temporarily stored in these locations. They are neurosecretory terminals.
What is the role of the posterior pituitary?
The posterior pituitary is not glandular as is the anterior pituitary. Instead, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary, and serve as a site for the secretion of neurohypophysial hormones (oxytocin and vasopressin) directly into the blood.
