Exam I Flashcards
Role of endocrine system
homeostasis
Main endocrine product
Hormones go directly into the interstitium or directly to the blood for affecting different target cells
Main endocrine product
Hormones
Hormones and Target Cells
hormones bind to specific receptors either on the surface or within the cells. They typically generate second messengers
Structural groupings of hormones
Peptides and proteins -
steroids - testosterone
amino acid derivatives - thyroid hormones, epinephrine
fatty acid derivatives - eicosanoids
features of endocrine systems
ductless, cells are epitheliod in appearance often arranged in cords or clusters, sparse CT, very vascular and often fenestrated (leaky) sinusoidal capillaries
hypophysis (pituitary gland) role
the relay station, feedback from target organs and the brain controls its responses
Developmental biology of hypophysis
1) neurohypophysis: downward extension form the floor of the hyothalamus (diencephalon)
2) adendohypophysis develops as a pouch-like ectodermal outpocketing of the oral cavity
(stomodeum) , it surrounds the neurohypophysis
Pictures in the notes
hypophysis (Pit. Gland) morphology
saddle-shaped depression of the sphenoid bone (sella turcica). It
has two distinct parts (neurohypophysis and adenohypophysis) with vascular connections. The two parts will be
covered individually followed by an explanation of the vascular connection.
Neurohypophysis (posterior lobe)
extension of the nervous system.
3 regions
median eminence, infundibular stalk, neural lobe
Stroma
astroglial-like stromal cell called pituicyte
Hypothalmic nuclei
neuron cell bodies in the parenchyma that produce the neurosecretory products
Neurosecretory products of parenchyma
The secretion is transported down their axons and stored within
axonal dilatations
stimulation of hypothalamic nerve bodies…
produces an axon potential that travels
down the axon and results in the release of the neurosecretion to nearby
(fenestrated) capillaries.
Adenohypophysis (anterior lobe)
has cells that are epitheliod (i.e.‘epithelial-like’) which
is understandable since it develops as an outpocketing of the oral cavity, an epithelial lined cavity.
3 regions
pars tuberalis, pars intermedia, pars distalis
pars tuberalis
Surrounds median eminence/ infundibular stalk. Very vascular (contains part of venous portal system vessels) Basophilic cells with melatonin receptors i.e. may have role in photoperiod regulation
Pas intermedia
Between pars distalis and neural lobe of neurohypophysis (large ruminants have ‘Wulzen’s cone’ i.e. pars distalis type cells) Basophilic cells (melanotropes) – produce melanocyte stimulating hormone. (hypothalmic control)
Pas distalis
Largest, most distal part of pituitary. Basophilic and acidophilic staining cells (hypothalamic control via a venous portal system)
Somatotrope
Growth hormone
PD
lactotrope (mammotrope)
prolactin
PD
Thyrotrope
TSH thyrotropin
PD
Corticotrope
corticotropin (ACTH)
PD
gonadotrope
FSH, LH
PD
Chromophobe
Possibly a degranulated cell
small, no granules
PD
melanotropes /Wulzen cone
Pale basophil
MSH
PI
cells with melatonin receptors (some gonadotropes and thyrotropes)
Pale basophil
have melatonin receptors playing a role in photoperiod effects of melatonin
PT
the hypophyseal (venous) portal system
connecting the neuro- and adenohypophysis
venous portal system = two veins with a capillary bed inbetween
HPS #1
transport of hypothalmic neurosecretions waiting inthe axonal dilitations in the median eminence/infundibular stalk region, to the pars distalis cells this is where they reach capillary beds and are released to the interstitium
HPS #2
Pars distalis cells are stimulated or inhibited to release their specific hormones into the
surrounding interstitium, these hormones are then transported into the general circulation
via veins draining the pituitary gland. Now these hormones can have a wide-range of
affects on distant targets.
Pineal gland morphology
cone shaped projection from roof of third ventricle
pineal gland development
This gland develops as a neuroectodermal evagination of the dorsocaudal part of the
diencephalon (epithalamus), located caudal to the anterior choroid plexus
Pineal gland anatomy
The stroma
consists of supportive glial cells.
A unique histological feature is corpora arenacea (“brain sand”), calcareous
concretions composed of calcium phosphates and carbonates, that increase with age
and may actually be seen on radiographs i.e., this can also serve as a useful clue for
identification of this organ on histological section
Parenchyma of pineal gland
pinealocytes and capillaries for easy up take and dissemination of their secretory product, MELATONIN. no blood brain barrier here
pinealocytes
acidophilic cell with many processes and a leptochromatic nucleus
melatonin
indoleamine: from tryptophan
Melatonin’s role is to inhibit the secretion of gonadotropin releasing hormone from
the hypothalamus – which results in a decrease production of hormones (e.g., FSH, LH) by the gonads.
affect seasonal trends and circadian rhythm
relaying light signal
In mammals the pineal is indirectly stimulated. The “light signal” is relayed from the retina to the suprachiasmatic
nucleus (hypothalamus) to the cranial cervical ganglion to the pineal via (postganglionic fibers which then directly
stimulate the pinealocyte to produce melatonin.)
lower vertebrates are directly stimulated
adrenal gland morphology
flattened triangular shaped, located at the cranial point of each kidney, cortex and medullary sections are apparent upon transection
Cortex of adrenal gland
develops from the urogenital area mesoderm
medulla of adrenal gland
develops from the neural crest ectoderm which migrates to the cortical tissues (vasculature linkage to cortex
stroma of adrenal gland
connective tissue capsule which extends septa
into the organ, carrying blood vessels and nerves to the medulla.
Parenchyma of Adrenal gland
cortex has ‘epitheliod’ shaped secretory cells organized into cords (two
cells thick) next to fenestrated capillaries. Hormones are not stored, rather they are released after synthesis.
Medulla has irregular shaped cells (modified postganglionic neurons) in close association to vessels.
Zona Glomerulosa (cortex of AG)
cell clusters or loops of cells.
H: mineralcorticoids
T: kidneys
A: sodium reabsorption, K excretion maintain balance
C: hypoplasia (addisons disease) results in sodium and fluid loss leading to shock and death
zona Fasciculata (middle largest cortical region AG)
radially arranged cell cords H: glucocorticoids in response to ACTH from pituitary gland T: many Action: metabolism and immunosuppression C: hyperplasia (cushings syndrome)
zona reticularis ( cortex of AG)
network of cell cords
H: glucocorticoids, weak androgens in response to ACTH
T: many
medulla of AG
cells are modified postganglionic neurons, innervated by preganglionic
sympathetic neurons.
H: NE, E
(methylation of NE leads to E)
The peripheral region of the medulla may have the
highest concentration of epinephrine containing cells e.g., ruminant, pig and
horse.
Dual artery supply to the medulla AG
direct: branches off the capsular artery
indirect: vessels draining cortex (adrenomedullary collecting vein)
the glucocorticoids produced in the cortex are carried to the medullary region stimulating the conversion of NE to E
Adrenal gland drainage
central adrenomedullary vein drain the entire gland
Thyroid gland morphology
shield shaped, unpaired with 2 lobes
Species variable appearance: single lobed
structure, lobes connected by an isthmus or totally separated lobes.)
thyroid gland development
endodermal outgrowth (foregut)
Thyroid gland stroma
capsule (thin) with CT septa into gland
Thyroid gland parenchyma
thyroid follicles (functional unit), a sphere-like cluster of
follicular cells resting on an outer basement membrane and surrounded
by sinusoidal capillaries and lymphatics. Cell height: variable, dependent
on cell’s activity level. Cell surface: microvilli. Additional cell type in
thyroid gland: parafollicular cells, located adjacent (or incorporated
into) thyroid follicles
hormone of follicular cells (TG)
thyroid hormone T3 and T4
Thyroid hormone
Hormone is stored within the thyroid follicle lumen (*colloid) until needed and release is stimulated by thyrotrope cells (thyroid stimulating hormone) of the adenohypophysis
Steps in synthesis and secretion of t3 and t4 (note)
chart in notes
Thyroid hormone Target and action
many cells and metabolic processes. ACTIONS: binds to receptor in cytoplasm
ligand/receptor complex then binds to thyroid hormone response elements in nuclear DNA activation of cellular DNA
upregulation of general protein synthesis and increased metabolic rate in target cells.
TH Clinical low
Low levels of TH depresses cellular metabolism causing immune destruction of the thyroid gland, iodine deficiency leading to inability to produce TH, body increases TSH (dog hypothyroidism)
Signs: depression of general activity level, weight gain
TH clinical high
Cats: hyperthyroidism (Grave’s disease) is more common then
hypothyroidism in cats. This condition can be due to a tumor of thyroid gland. Signs: weight loss but voracious appetite
parafollicular cell
develop: neural crest origin pale, acidophilic cytoplasm, many mitochondria and small membrane bound granules. Located throughout the thyroid gland [within the follicular basement membrane (singly) and between follicles (in clusters)]. H: CALCITONIN decrease blood Ca
Parathyroid gland morph and development
pair associated with each lobe of the thyroid (4)
derivation from the 3rd and 4th pharyngeal pouch endoderm
Parathyroid gland stroma
capsule comprised of thin CT surrounds each gland
Parathyroid gland parenchyma
mainly small cells (in clusters or cords) called the Chief (or
principal) cells. These cells secrete parathyroid hormone. [Dark Chief cells are metabolically active (basophilic
cytoplasm) and have nuclei with condensed chromatin. Light Chief cells are inactive or depleted of granules.]
parathyroid gland etc,
H: parathyroid hormone
helps to control blood Ca levels (detect and stimulate)
. CLINICAL: high levels (hyperparathyroidism) SIGNS: calcium deposits in blood
vessels, heart, kidneys, AND osteoporosis. Low levels (hypoparathyroidism). SIGNS: nerve hyperexcitability, muscle
spasm and tetany.
APUD
Amine Precursor Uptake and Decarboxylation (the diffuse neuroendocrine system)
APUD Info
Single cells or small clusters located throughout the body
Paracrine and autrocrine routes to transfer multiple hormones
H: biologically active amines
Amine precursors uptake intracellular decarboxylation biologically active amines.
Hormone products - stored (vesicles)
Exocrine pancreas
85% of the pancreas and secretes digestive enzymes, water, NaHCO3 into the duodenum
Exocrine pancreas Stroma
Sparse stroma (investing CT) very thin capsule and delicate CT septa that divide the gland into many distinct lobes
Ex. Pancreas Parenchyma
functional part of the organ. contains:
acinus
acinar cells
centroacinar cells
acinus
the main functional pancreatic unit
responsible for synthesizing and secreting enzymes and proenzymes. Each acinus is comprised of about 50 acinar cells within a
basal lamina. There are no myoepithelial cells in pancreas
acinar cells
are highly polarized and pyramidal in shape with basal
nuclei and abundant RER; apical, membrane bound zymogen granules are evident.
centroacinar cells
pale, cuboidal cells with elongated central nuclei and abundant mitochondria located in the center of the acini;
(they secrete water and electrolytes and are the first cells of the intercalated ducts. They are difficult to visualize in histological sections
Ex. Pancreas Duct system
intercalated ducts, intraloular ducts, interlobular ducts
intercalated ducts pancreas
exit of centroacinar cells composed of low cuboidal or simple squamous epithelium secretes large amounts of bicarbonate ions which neutralize acid from the stomach
intralobular ducts (pancreas)
made from several fused intercalated ducts. their epithelium is still cuboidal (Pancreas has no striated ducts)
interlobular ducts
found in stromal C.T. leading to the main
duct, which may be lined by columnar epithelium. The main duct
runs the length of the gland and pierces the wall of the duodenum.
Pancreas storage
enzymes and zymogen synthesized in acinar and stored in granules
Zymogen
granules accumulated at apex of acinar cell when the cell is stimulated by a hormonal signal or a nerve impulse,
the contents of the granules are released into a duct leading into theduodenum.
Pancreatic juice
enzymes that digest the main components of ingested food.
Zymogen enzymes are inactive
proenzymes, which are activated by specific proteolytic cleavages
within the duodenum. These are carried to the duodenum along with
water, electrolytes and bicarbonate (HCO3
General islets
Endocrine
islet parenchymal cells are derived from the endoderm of the developing duodenum
Pancreatic islets
endocrine
are
scattered throughout the exocrine pancreas with cells arranged in
cords or clusters and occupy 1-2% of pancreatic volume.
Endocrine pancreas stroma
sparse reticular CT
Endo. pancreas parenchyma
several types of cells in cords or clusters these are islet cells 4 that secrete polypeptides
Alpha islet cells
produce and release glucagon (10-20% of islets)
Beta islet cells
Produce and release insulin (60 - 75% islet )
delta islet cells
produce and release somatostatin (4-6% islet)
PP cells
produce and release pancreatic polypeptide 2%
Fenestrated capillaries
have pores thta open directly between vascular spce and the capillary basement membrane (endocrine glands one of the few places that these form)
leads to rapid diffusion into the circulatory system (not big enough for platelets
Islet hormone major targets
anabolic actions of insulin: liver, adipose, and muscle.
need to have insulin cell receptors.
insulin in liver
promote glycogen synthesis with glycogen synthetase (inhibiting glycogen phosphorylase)
insulin in muscle and adipose
uptake of glucose through GLUT4.
muscles make glycogen and adipose makes FA for triglyceride storage
insulin in muscles
stimulate uptake of AA. suppress mobilization of fuels (no breakdown of glycogen in liver, release of AA or FA)
Role of Female System
production of ovum, secretion of hormones, a conduit for transport of
sperm, environment for embryo/fetal development and a means for parturition.
Ovary morph
oval shaped with indentation (hilus) where nerves and vessels enter and exit
Ovary Stroma
Dense connective tissue
capsule (tunica albuginia) covered with tunica serosa
(visceral peritoneum). Connective tissue support
throughout organ, large vessels in medullary region
Ovary parenchyma cortex
contain ovarian follicles and cords of cells (cortical cords). endocrine cells between the follicles that produce estrogen
ovary parenchyma medula
embryonic remnants arranged as cords of cells (medullary cords) some with a small cavity (rete ovarii)
mare difference ovary
mare cortex and
medulla are reversed i.e. medullary tissue surrounds most of cortical tissue except in an indented
region the ovulation fossa (ovulation site).
ovary development
primordial germ cells migrate from the yolk sac to the gonadal ridge .
PGC mitotic division result in lifetime supply of ovuum at birth.
meiosis: arrested at the primary oocyte stage with a single flattened layer of surrounding follicular cells (primordial follicle)
develop when chosen after puberty
ovarian follicle steps
oocyte, follicular cells, ovulation, Corpus Luteum, CL degrade to Corpus albicans
primordial follicle
inactive single layer of flattened follicular cells
primary follicle
1st active stage, a single layer cuvoidal follicular cell. Zona Pellucida beginning to form.
secondary follicle
2 or more layers of follicular cells (stratum granulosa layer). obvious: zona Pelucida, outer basement membrane and thecal layers
tertiary follicle
antral growing (graffian follicle) same layers as secondary follicle, but more
elaborate. NEW features (1) follicular antrum (cavity); (2) cumulus oophorus a ‘cloud’ of follicular cells that
remains associated with the primary oocyte, the innermost cells are called the corona radiata.
Estrogen production follicles
larger follicles produce Estrogen to prime the uterus to receive a fertilized egg. secretion of uterine “milk” to supply the egg with nutrients
Steps of Estrogen production
2-cell gonadotropin model: LH binds theca interna cells stimulating testosterone production. T diffuses into the stratum granulosum layer.
Granulosa cells receive FSH making enzymes to convert T to estradiol
follicle fate
degeneration
ovulation
corpus luteum formation
luteolysis
follicle degeneration
nucleus condenses or breaks apart, basement membrane components may
thicken. Degeneration can happen at any stage e.g. small follicles may reabsorb completely, large
follicles may be replaced by a ‘scar’
follicular ovulation
tertiary follicle rupture and the release of antral fluid plus oocyte. The
will float into the uterine tube, where it may encounter sperm. If fertilization occurs the zygote will
float toward the uterus. Unfertilized ovum will degenerate.
Follicular CL
Post-Ovulation corpus hemorrhagicum corpus luteum.
bloody clot formation of tert. follicle due to rupture, stromal cells remove clot, The follicle wall remnants and surrounding theca interna cells transform into steroid-secreting
cells (luteinization) and are now termed “luteal cells”. The corpus luteum (CL) produces progesterone,
this hormone stimulates uterine glands to secrete and hinders uterine contractions to support the fertilized egg and allow attachment
follicular luteolysis
CL no longer needed (not pregnant) prostaglandins will be produced by the uterus and result in luteolysis
prostoglandin depends on species
most: produced in uterus and transported through venous drainage and entire system to reach CL.
Sow, ewe, cow: passive transport from venous drainage into adjacent ovarian artery (counter exchange) avoid breakdown in system
follicular phase
follicules main with estrogen produced.
priming for breeding (estrus)
luteal phase
CL main with progesterone produced.
post ovulation: prepare for fertilization and implantation. enrich the environment. no fertilization: luteolysis
tubular organs of females
same layers found in typical tubes : tunica mucosa
tunica submucosa
tunica muscularis
tunica serosa/advenitia
tunica mucosa
epithelium, lamina propria (CT), muscularis mucosa(smooth muscle)
muscle layer separates from next layer
Tunica submucosa
referred to as t. mucosa/submucosa. Glands may be present
tunica muscularis
may be composed of smooth or skeletal muscle, depending on the specific tubular organ
tunica serosa/adventitia
indicates the presence or absence of an outer serosal covering (dependent on tubular organ you’re dealing with
Key female repro features
luminal epithelium (simple columnar with cilia or not or stratified squamous). Wall features: glands in the t. muc./submuc.? t. muscularis have smooth or skeletal muscle?
key features chart
in notes look at it
events in the female tubes
After fertilization of the ovum within the uterine tube and initial cleavage within this tube, the resultant
blastocyst floats to the uterus. Within the uterine lumen the secretions from the glands in this region
(“uterine milk”) provide the needed initial nourishment to this developing embryo.
Placenta
union of extraembryonic membranes (chorion and allantois) with portions of the uterine
lining cells/wall to create an area of metabolic exchange (nourishment and waste removal) in addition to the
production of hormones important for pregnancy and parturition.
nondeciduate or deciduate (shed)
Deciducate type of placentation
will shed a part of endometrium
during parturition
Chorionic fold distribution
the pattern of contact between fetal and maternal tissue
fetal/maternal blood separation
the materna layer that the chorion is apposed to
vagina
site for insemination in most species, monitor heat cycles from vaginal swabs
vestibule/vulva
st. squamous with erectile tissue and mucosal glands (vestibule). dense vascular plexus (vulva)
T. muscularis has smooth and skeletal
clit
penis homologue paired erectile tissue
female urethra
open at vag. vest. junction.
epithelium: transitional changing to stratified cuboidal-columnar and the stratified squamous near external urethral orifice.
L.propria/submucosa with erectile tissue (endothelial lined cavernous spaces may be prominent)
T. muscularis: several ill-define layers; smooth muscle proximally, skeletal muscle (urethralis m.) near the external urethral orifice
Scrotum
skin pouch with 2 cavities lined with parietal vaginal tunic, each containing a testis. tunica dartos (sm. muscle in wall) regulate temp and position
testis
covered with visceral vaginal tunic
testis stroma
CT blends with dense irrecular CT of testicular capsule (tunica albuginea).
Septa subdivides testes into lobes
Testis parenchyma
germinal epithelium of tubes and interstitial endocrine cells
Interstitial endocrine cells (leydig cells)
produce testosterone and lay between testicular ducts
intra testicular ducts
convoluted seminiferous tubules (CST) straight tubules (ST) rete testis (RT) and this connects to the extra testicular duct
extra testicular duct
efferent ductules epididymal duct ductus deferens
convoulted seminifersous tubules (CST)
stratified
epithelium containing cells related to sperm formation and
supportive (sustentacular) cells (details below). Many coiled
loops of tubules fill the testis
straight tubules
small section of duct (only sustentacular cells) connects CST to RT
Rete tubules
last portion of intra. test. ducts connects to epididymis
simple cuboidal - columnar
CST stroma
tubules surrounded by basal lamina and peritubular contractile cells. contraction moves sperm and secretes out tubes
CST parenchyma
sustentacular (sertoli) cells
several types of spermatogenic cells
sustentacular cells
have a large nucleus with a prominent nucleoli; cytoplasmic processes surround
developing spermatogenic cells; tight junctions connect cells to each other. FUNCTION: nourish,
support spermatogenic cells; synchronize spermatogenesis; form blood testis barrier
blood testis barrier
tight junctions between adjacent sustentacular and serves to compartmentalize the
epithelium into basal and adluminal (apical) compartments. Tissue fluid has relatively free access to the
basal compartment but not to the apical compartment where meiosis and spermiogenesis occur
spermatogenic cells
stratified in epithelium according to stage of development/differentiation
Spermatogenesis
spermatocytogenesis, meiosis, spermiogenesis
spermatocytogenesis
multiple mitotic divisions of
spermatogonia primary spermatocyte Cell moves to
adluminal compartment.
meiosis of spermatogenesis
1 primary spermatocyte (4N) 2 secondary
spermatocytes (2N) 4 spermatids (1N)
spermiogenesis
transformation of round spermatid to elongate sperm. form acrosome (enzyme cap). condense nucleus, lose cytoplasm and form motile tail
epididymis morph
head, body, tail
epididymis stroma
visceral vaginal tunic and a dense irregular CT covering
Epididymis parenchyma
efferent ducts: from RT.
become one coiled ductus epididymis in head region and tail is continuous with ductus deferens
efferent ductules:
tubules with CT and contractile cells. cilia to move the sperm long and non ciliated to reabsorb fluid
ductus epididymis
head to body to tail increase in smooth muscle.
Epithelium: PSc with long branched microvilli often matted together. they resorb most fluid that leaves the testes
sperm storage
tail of epididymis
transit takes 10 to 15 days
ductus deferens morph
straight tube continuation of epididymis. opens into urethra at the prostate
DD stroma
multiple layers of Sm m.
DD parenchyma
PSC epithelium with microvilli to SC
some species have accessory glands at the end called ampulla
Acessory gland
produce the seminal plasma providing nutrients, transport, cleaning, lubrication
has SM. m. that squeezes to secrete the gland
4 accessory male organs
ampulla, vesicular, prostate, bulbourethral
chart of who has what in the notes
Prostate who has what
all have HRPDC
bulbourethral who has what
HRPC have and dog doesnt
prostate gland
body: at the level of colliculus seminalis (around or on top of )
disseminate can only see microscopically
Prostate gland Stroma
capsule with DICT and sm. m.
skeletal urethralis m. may surround disseminate
prostate gland parenchyma
cuboidal columnar. disseminate - mucous type glands deep to mucosa
urethra
tube for urine outflow
pelvic urethra
portion in pelvic canal has pre and post prostatic parts possible
penile urethra
close to the bladder is sm. m. (internal urethral sphincter)
sk. m. (external urethral sphincter) of distal urethra. transitional epithelium. may have mucosal
Penis
root, body, free part
fibroelastic penis
stiff, nonexpansile, has sigmoid flexure which straightens for elongation
musculovascular
flexiblie with expansion due to blood flow and stiffening (horses and dogs)
Erectile tissue
dense collagenous CT with elastic
helicine arteris with longitudinal sm. m. in tunica interna resulting in an irregular outline.
relaxation allows blood flow into the erectile tissue
identifiable features ofr root body and free part
in notes
