0x Histology of the Endocrine System Lecture Flashcards Preview

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Flashcards in 0x Histology of the Endocrine System Lecture Deck (45):
1

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

2

parenchyma

the functional tissue of an organ

3

stroma

the connective tissue or framework of an organ

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

4

capsule

part of the stroma; surrounds the gland

5

trabeculae

part of the stroma; septa

divide glands into loves or lobules

6

lumen

the inner open space or cavity of a tubular organ

7

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

8

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

9

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

10

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

11

name endocrine organs/glands

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

ovaries and testes
placenta
gastrointestinal tract

12

what are the 2 lobes of the pituitary

anterior pituitary - adenohypophysis
posterior pituitary - neurohypophysis

13

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)

14

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)

15

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

AP - hypophysial portal system
PP - hypothalamo-hypophysial tract

16

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

17

What are the parts of the anterior pituitary

pars tuberalis
pars intermedia
pars distalis

18

What are the parts of the posterior pituitary

infundibular stalk
pars nervosa

19

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

20

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

21

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

pars distalis

very vascular contains huge sinusoidal capillaries

22

residual lumen

embryologic artifact of the Rathke's Pouch

23

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

24

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

huge sinusoidal capillaries

25

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

basophilic cuboidal cells
- melanocytes → MSH

26

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

27

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

axons
- contain secretory granules
- whispy appearance

pituicytes
- might function as neuroglia

28

epiphysis cerebri

pineal gland

29

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

produces melatonin and serotonin

30

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

31

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

32

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"

33

Describe the cell types found in the thyroid gland

follicles lined with follicular cells containing colloid

parafollicular cells between the follicular cells

34

What does colloid produce? Where?

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

35

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

36

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

37

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

38

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

39

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

40

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

41

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

42

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

freely anastomosing cells

sex steroids (DHEA); precursor to testosterone and estradiol

43

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

44

Describe the gross anatomy of the pancreas

both exocrine (majority) and endocrine

Islets of Langerhans = endocrine cells embedded in exocrine tissue

45

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)