0x Histology of the Endocrine System Lecture Flashcards
endocrinology
a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions called hormones
the integration of developmental events such as proliferation, growth, and differentiation (including histogenesis and organogenesis) and the coordination of metabolism, respirations, excretion, movement, reproduction, and sensory perception dependent of chemical cues, substances synthesized and secreted by specialized cells
parenchyma
the functional tissue of an organ
stroma
the connective tissue or framework of an organ
contains blood vessels, nerves, trabeculae, and finer fiberous networks of collagen (reticular fibers) or elastin
capsule
part of the stroma; surrounds the gland
trabeculae
part of the stroma; septa
divide glands into loves or lobules
lumen
the inner open space or cavity of a tubular organ
exocrine vs endocrine
exocrine release: through ducts
- ex: sweat glands, salivary glands, mammary glands, pancreas, liver
endocrine release: directly into blood vessels or lymph
- ex: adrenal glands, testes, ovaries, pancreas
basic exocrine gland development
(starts the same as endocrine)
1) specific loci in epithelium begin to proliferate
2) dividing cells invade underlying stroma but retain “seperateness” via basal lamina
(differs here)
3) tubular duct system develops
4) remaining cells differentiate into secretory cells
basic endocrine gland development
(starts the same as exocrine)
1) specific loci in epithelium begin to proliferate
2) dividing cells invade underlying stroma but retain “seperateness” via basal lamina
(differs here)
3) connection with the surface is lost
4) secretory cells associate with blood capillaries or sinuses
describe the release of endocrine hormones and the 3 methods of action
hormone diffuses from the extracellular fluid into the bloodstream and then acts as:
endocrine - travels through the body
paracrine - acts on nearby cells/tissues
autocrine - acts on itself
name endocrine organs/glands
hypophysis cerebri - pituitary epiphysis cerebri - pineal body thyroid parathyroid adrenal pancreatic islets of langerhans
ovaries and testes
placenta
gastrointestinal tract
what are the 2 lobes of the pituitary
anterior pituitary - adenohypophysis
posterior pituitary - neurohypophysis
Describe the basic development of the adenohypophysis
1) ectoderm from the rood of the stromadeum (oral cavity) forms Rathke’s pouch
2) base of Rathke’s pouch constricts, separating it from the oral cavity
3) lumen of Rathke’s pouch may persist as the residual lumen
(the AP and PP meet and fuse to form the Pituitary)
Describe the basic development of the neurohypophysis
1) neuroectoderm of the ventral wall of the diencephalon evaginates to form the infundibulum
2) lumen of 3rd ventricle extends into infundibular stalk and persists as the infundibular recess in some species (pig, cat)
(the AP and PP meet and fuse to form the Pituitary)
what are the 2 distinct systems by which the hypothalamus communicates with the pituitary gland
AP - hypophysial portal system
PP - hypothalamo-hypophysial tract
Describe the hypophyseal portal system.
in the hypothalamus parvocellular neurons in secrete hypothalamic releasing or inhibiting factors (prohormones)
which travel down through the portal vein and are released into the paracapillary space in the adenohypophysis (anterior pituitary)
where they trigger release of other hormones that travel out to the body through the vein
What are the parts of the anterior pituitary
pars tuberalis
pars intermedia
pars distalis
What are the parts of the posterior pituitary
infundibular stalk
pars nervosa
Describe the hypothalamo-hypophysial tract
cell bodies of the magnocellular neurons in the hypothalamus produce prohormones and package them into granules with converting enzymes
they then travel down the unmyelinated axons into the neurohypophysis and accumulate in Herring bodies in the pars nervosa until release is stimulated
What are the 2 types of endocrine producing neuron cell bodies in the hypothalamus? What do they produce?
1) supraoptic nucleaus produces ADH (vassopressin)
2) parventricular nucleus
produces oxytocin
what is generally the largest part of the pituitary gland across species
pars distalis
very vascular contains huge sinusoidal capillaries
residual lumen
embryologic artifact of the Rathke’s Pouch
What are the 3 cells types in the pars distalis of the adenohypophysis
1) Chromophobes
- do not stain well
- function unknown; degranulated
2) Chromophil - Acidophils (tan)
- somatotrophs → GH
- lactotrophs → prolactin (PRL)
3) Chromophil - Basophils (blue)
- thyrotrophs → thyroid stimulating hormone (TSH)
- gonadotrophs → FSH / LH
- corticotrophs → ACTH
What is a major marking characteristic of the pars distalis of the anterior pituitary?
huge sinusoidal capillaries
What are cells are found in the Pars Intermedia of the adenohypophysis?
basophilic cuboidal cells
- melanocytes → MSH
What are cells are found in the Pars Tuberalis of the adenohypophysis?
weakly basophilic cells
- function unknown
- do stain weakly for ACTH, FSH, and LH
also large vessels that are part of the hypophyseal portal system
What are cells are found in the Pars Nervosa of the neurohypophysis?
axons
- contain secretory granules
- whispy appearance
pituicytes
- might function as neuroglia
epiphysis cerebri
pineal gland
What is the function of the epiphysis cerebri “pineal gland”
produces melatonin and serotonin
What inhibits melatonin and serotonin production in the pineal gland?
light
mammals receive information on light indirectly via the retina
parietal eyes are found in some lizards, frogs, lampreys, and fish “third eye” can directly sense light
What are the cell types found in the pineal gland
pinealocytes
- neuroepithelial origin; photo receptors in non-mammalian vertebrates
- large round nucleus; acidophilic cytoplasm
- produce melatonin
astrocytes
- interstitial cells
- compressed nuclei; darker cells
Corpora aranacea
- brain sand; Ca deposit
- stains basophilic
- extracellular, increases with age, not considered pathological
Describe the gross anatomy of the thyroid gland
lies on the trachea just caudal to the larynx
lobes may be connected by an isthmus (fused in pigs)
“Goiter”
Describe the cell types found in the thyroid gland
follicles lined with follicular cells containing colloid
parafollicular cells between the follicular cells
What does colloid produce? Where?
takes up iodine from the system and produced T3 and T4 in the thyroid gland
Describe the gross anatomy of the parathyroid gland
generally 4 small glands located about the cranial trachea
generally there are 2 internal glands embedded within the thyroid glands and 2 external glands are outside the thyroid tissue
What are the cell types found in the parathyroid gland
cells are arranged in cords
Chief cells → parathormone → increases blood calcium
Oxyphil cells
- hard to find - cytoplasm is stains diff. sort of smooth
- occur in oxen, horses, man
- unknown function but # often increase w/ age
Describe the gross anatomy of the adrenal gland from outside in.
capsule = skin cortex = fruit medulla = seed
may be attached or detached from the kidney depending on species
What are the cellular layers of the adrenal gland from the outside in
capsule cortex 1) zona glomerulosa (ruminants, primates) / zona arcuata (horses, carnivores, pigs); SALT 2) zona fasciculata; SUGAR 3) zona reticularis; SEX adrenal medula
Describe the blood supply of the adrenal gland
several major arteries branch into a plexus of arterioles under capsule, then there are 3 systems
1) subcapsular capillary plexus drains in the subcapsular veins
2) cortical blood sinusoids drain to medullary veins
3) medullary arteries from capillary bed in medulla that drains to medullary veins
What are the characteristics zona glomerulosa (ruminants, primates) or zona arcuata? What does it produce?
steroid producing cells; lipid droplets, tubular mitochondria, extensive smooth endoplasmic reticulum
mineralcorticoids (aldosterone) → increases sodium resporption
What are the characteristics zona fasciculata? What does it produce?
characteristic morphology is radially arranged cords of parenchyma cells
cuboidal cells (spongiocytes) → glucocorticoids → cortisol increases blood glucose & acts on the medulla of the adrenal gland
What are the characteristics zona reticularis? What does it produce?
freely anastomosing cells
sex steroids (DHEA); precursor to testosterone and estradiol
What are the characteristics medulla of the adrenal gland? What does it produce?
distinct border between zona reticularis and medulla
chromaffin cells
- modified postganglionic sympathetic nerve cells, regulated by sympathetic ganglion cells and steroids of adrenal cortex
- produce catecholamines, epinephrine, norepinephrine
Describe the gross anatomy of the pancreas
both exocrine (majority) and endocrine
Islets of Langerhans = endocrine cells embedded in exocrine tissue
What are the Islets of Langerhans and what cells do they contain?
the endocrine portion of the pancreas
α-cells → glucagon → increases blood glucose
β- cells → insulin → decreases blood glucose; 75% of Islets of Langerhans
δ-cells → somatostatin → inhibits secretion of glucagon and insulin
F (PP) - cells → pancreatic polypeptide (more abundant in chickens)
