0x Histology of the Endocrine System Lecture

Question 1

endocrinology

Answer 1

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

Question 2

parenchyma

Answer 2

the functional tissue of an organ

Question 3

stroma

Answer 3

the connective tissue or framework of an organ

contains blood vessels, nerves, trabeculae, and finer fiberous networks of collagen (reticular fibers) or elastin

Question 4

capsule

Answer 4

part of the stroma; surrounds the gland

Question 5

trabeculae

Answer 5

part of the stroma; septa

divide glands into loves or lobules

Question 6

lumen

Answer 6

the inner open space or cavity of a tubular organ

Question 7

exocrine vs endocrine

Answer 7

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

Question 8

basic exocrine gland development

Answer 8

(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

Question 9

basic endocrine gland development

Answer 9

(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

Question 10

describe the release of endocrine hormones and the 3 methods of action

Answer 10

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

Question 11

name endocrine organs/glands

Answer 11

hypophysis cerebri - pituitary
epiphysis cerebri - pineal body
thyroid
parathyroid
adrenal
pancreatic islets of langerhans

ovaries and testes
placenta
gastrointestinal tract

Question 12

what are the 2 lobes of the pituitary

Answer 12

anterior pituitary - adenohypophysis

posterior pituitary - neurohypophysis

Question 13

Describe the basic development of the adenohypophysis

Answer 13

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)

Question 14

Describe the basic development of the neurohypophysis

Answer 14

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)

Question 15

what are the 2 distinct systems by which the hypothalamus communicates with the pituitary gland

Answer 15

AP - hypophysial portal system

PP - hypothalamo-hypophysial tract

Question 16

Describe the hypophyseal portal system.

Answer 16

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

Question 17

What are the parts of the anterior pituitary

Answer 17

pars tuberalis
pars intermedia
pars distalis

Question 18

What are the parts of the posterior pituitary

Answer 18

infundibular stalk

pars nervosa

Question 19

Describe the hypothalamo-hypophysial tract

Answer 19

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

Question 20

What are the 2 types of endocrine producing neuron cell bodies in the hypothalamus? What do they produce?

Answer 20

1) supraoptic nucleaus 
produces ADH (vassopressin)

2) parventricular nucleus
produces oxytocin

Question 21

what is generally the largest part of the pituitary gland across species

Answer 21

pars distalis

very vascular contains huge sinusoidal capillaries

Question 22

residual lumen

Answer 22

embryologic artifact of the Rathke’s Pouch

Question 23

What are the 3 cells types in the pars distalis of the adenohypophysis

Answer 23

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

Question 24

What is a major marking characteristic of the pars distalis of the anterior pituitary?

Answer 24

huge sinusoidal capillaries

Question 25

What are cells are found in the Pars Intermedia of the adenohypophysis?

Answer 25

basophilic cuboidal cells | - melanocytes → MSH

Question 26

What are cells are found in the Pars Tuberalis of the adenohypophysis?

Answer 26

weakly basophilic cells - function unknown - do stain weakly for ACTH, FSH, and LH also large vessels that are part of the hypophyseal portal system

Question 27

What are cells are found in the Pars Nervosa of the neurohypophysis?

Answer 27

axons - contain secretory granules - whispy appearance pituicytes - might function as neuroglia

Question 28

epiphysis cerebri

Answer 28

pineal gland

Question 29

What is the function of the epiphysis cerebri "pineal gland"

Answer 29

produces melatonin and serotonin

Question 30

What inhibits melatonin and serotonin production in the pineal gland?

Answer 30

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

Question 31

What are the cell types found in the pineal gland

Answer 31

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

Question 32

Describe the gross anatomy of the thyroid gland

Answer 32

lies on the trachea just caudal to the larynx lobes may be connected by an isthmus (fused in pigs) "Goiter"

Question 33

Describe the cell types found in the thyroid gland

Answer 33

follicles lined with follicular cells containing colloid parafollicular cells between the follicular cells

Question 34

What does colloid produce? Where?

Answer 34

takes up iodine from the system and produced T3 and T4 in the thyroid gland

Question 35

Describe the gross anatomy of the parathyroid gland

Answer 35

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

Question 36

What are the cell types found in the parathyroid gland

Answer 36

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

Question 37

Describe the gross anatomy of the adrenal gland from outside in.

Answer 37

``` capsule = skin cortex = fruit medulla = seed ``` may be attached or detached from the kidney depending on species

Question 38

What are the cellular layers of the adrenal gland from the outside in

Answer 38

``` capsule cortex 1) zona glomerulosa (ruminants, primates) / zona arcuata (horses, carnivores, pigs); SALT 2) zona fasciculata; SUGAR 3) zona reticularis; SEX adrenal medula ```

Question 39

Describe the blood supply of the adrenal gland

Answer 39

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

Question 40

What are the characteristics zona glomerulosa (ruminants, primates) or zona arcuata? What does it produce?

Answer 40

steroid producing cells; lipid droplets, tubular mitochondria, extensive smooth endoplasmic reticulum mineralcorticoids (aldosterone) → increases sodium resporption

Question 41

What are the characteristics zona fasciculata? What does it produce?

Answer 41

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

Question 42

What are the characteristics zona reticularis? What does it produce?

Answer 42

freely anastomosing cells sex steroids (DHEA); precursor to testosterone and estradiol

Question 43

What are the characteristics medulla of the adrenal gland? What does it produce?

Answer 43

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

Question 44

Describe the gross anatomy of the pancreas

Answer 44

both exocrine (majority) and endocrine Islets of Langerhans = endocrine cells embedded in exocrine tissue

Question 45

What are the Islets of Langerhans and what cells do they contain?

Answer 45

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)