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Flashcards in Histology Deck (79):
1

Define endocrine cells

Specialized cells which secrete substances which affect other cells

2

What are the 5 major endocrine glands?

Pituitary, thyroid, parathyroid, adrenal, endocrine pancreas (islets)

3

What are the common features of endocrine tissues?

Ductless, vascular, organized into blocks/plates/cords, epithelial, polyhedral (cuboidal with prom cell borders), numerous organelles

4

What are the 5 characteristics of endocrine cells?

Specialized for secreting, secrete into interstitial fluid and then into bloodstream, do not require ducts, req proximity to blood vessels so they have a fine vascular network, fenestrated endothelium to allow for easy diffusion for larger mcs

5

What are the 4 patterns of endocrine cells

Epithelial
Mesenchymal
Neural
Individual cells

6

Which organs have an epithelial growth pattern?

Thyroid
Parathyroid
Ant pit
Adrenal cortex
Panc islets

7

What is the organization of epithelial endocrine cells?

Arranged in cords/clumps
Cells are attached to e.o
Ecto or endodermally derived (exception: adrenal cortex which is mesodermal)

8

What organs have a mesenchymal endocrine cells?

Leydig cells and ovarian stromal cells, granulosa and luteal cells

(connective tissue organization)

9

What are neural endocrine cells dervied from?

Neural crest

10

Where are neural endocrine cells?

Post pit
Adrenal medulla

11

What is the organization of the post pit

Organization of nervous system tissue
Secretory cells are supported by glial cells
-->neural endocrine cells

12

Describe the adrenal medulla

Sympathetic ganglion originate from neural crest and is innervated by preganglionic sympathetic axons

Lack axons, but function similar to sympathetic axons

-->neural endocrine cells

13

Where are individual endocrine cells?

Enteroendocrine cells of the GI tract which make a host of substances like gastrin and somatostatin

Also have neuroendocrine cells throughout the body

Juxtaglomerular cells (modified smooth muscle) of the renal cortex which make renin

14

Where is the pituitary located?

BAse of brain in sella tucica

15

What are the 2 parts of the pituitary? Where do they develop from?

Anterior: oral ectoderm
Posterior: neuroectoderm at the floor of the third ventricle

16

What can enlargement of the pituitary cause?

Visual disturbances due to prox to optic chiasm

17

Which part of the pituitary is the master gland?

Anterior: regulates most endocrine organs

18

What properties does the ant pituitary have?

Glandular and epithelial

19

What hormones does the ant pituitary secrete?

GH, prolactin, LH, FSH, TSH, ACTH

20

What regulates the ant pituitary?

Factors secreted by hypothalamic neurons

21

What is another name for the ant pituitary?

Adenohypophysis

22

What is another name for the post pituitary?

Neurohypophysis

23

What is the structure of the post pituitary?

Secretory endings of axons from nerve cells whose cell bodies are located in the hypothal

24

What hormones does the post pituitary secrete?

Oxytocin and ADH

25

What are the 3 parts of the ant pit

1. Pars distalis
2. Pars intermedia
3. Pars tuberalis

26

Describe the pars distalis

Bulk of anterior pit, arises from thickened ant wall of the RP

Cystic spaces filled with eosinophilic material

27

Describe pars intermedia

Remnant of post wall of RP

Basophilic

28

Describe pars tuberalis

Arises from thickened lateral wall of RP, forms sheath around infundibulum

Contains veins from hypothalamus/thalamus

29

What are the parts of the post pit.?

1. Pars nervosa
2. Infundibulum

30

Describe the pars nervosa

Contains neurosecretory axons and their endings

Biggest part of post pit

31

Describe infundibulum

Contains neurosec axons forming the hypothalamohypohysial tracts

32

What are the cell types of the pars distalis?

1. Chemophils ( 2 kinds: acidophils and basophils)
2. Cromophobes

33

What do acidophils produce?

GH (50% of cells) and PRL

34

What do basophils produce?

ACTH, LH/FSH, TSH

35

What are the subtypes of acidophils?

Somatotropes (GH) and LActotropes (PRL)

36

What are the subtypes of basophils?

Corticotropes (ACTH), Gonadotropes (LH/FSH) and Thyrotropes (TSH)

37

What is the neurohypophysis?

Another name for posterior pituitary, includes median eminence, infundibular stalk, pars nervosa

38

What is the pars nervosa made of?

Unmeylinated nerve axons (cell bodies in hypothal) and supportive cells called pituicytes)

39

What does the pars nervosa secrete?

ADH (synth by neurons in supraoptic nuc) and oxytocin (synth in neurons in paraventricular nuc)

40

How do pars nervosa nerve endings differ from normal ones?

1. Non-synaptic
2. Secrete hormones rather than NTs

41

What are the support cells of the pars nervosa?

Pituicytes (glial cells)

42

What does the pars nervosa do?

Serves as storage site for hormones which are stored in granules at axon terminals which are visible in light microscope as HERRING bodies

43

What are herring bodies?

Granules with hormones in them in the pars nervosa

44

What are the 4 parts of the thyroid?

Right lobe, left lobe, isthmus, pyramidal lobe

45

Describe the follicles of the thyroid gland

Colloid (extracellular thyroglobulin) accumulates in the follicles which are the extracellular storage of secretory products (this is unique in the thyroid). It has a large lumen surrounded by simple cuboidal epithelium

46

What do the follicular cells store thyroglobulin for?

Store in follicles for subsequent use in production and secretion of T3 and T4

47

What are parafollicular cells?

Also called C cells, produce calcitonin

48

What is each gland surrounded by?

Connective tissue capsule

49

Where do capillaries run in thyroid?

Between adjacent follicular walls (each follicle is surrounded by a capillary network)

50

Where are parafollicular cells? What do they look like?

Interstitium, appear as pale staining cells occurring in isolation or small clusters

Larger than follicular cells

Hard to see

51

What is the most common pathology thyroid is removed for?

Nodules

52

What is the parathyroid?

There are about 4 of them, they are small, they sit behind the thyroid, they regulate Ca metabolism. 10% are within the thymus

53

What is the parathyroid derived from?

Lower glands derived from 3rd branchial arch (like thymus)

Upper glands derived from 4th branchial arch

54

Describe the parathyroid capsule

Thin, fibrous capsule that forms septae that divides the gland into lobules. The lobules separate densely packed cords of cells.

55

Describe fat in parathyroid

Fat cells in thyroid increase with age eventually fat makes up 60-70% of gland.

56

Describe the blood supply of parathyroid

Rich vascular network with fenestrated capillaries

57

What are the 3 types of parenchymal cells (ie functional cells) of the parathyroid?

1. Principal/chief cells that secrete PTH (most numerous, present before birth)
2. Oxyphil cells (unknown fxn, larger and acidophilic)
3. Adipocytes (inc with age)

58

Describe parathyroid chief cells

Centrally located nuc, cytoplasm has glycogen, lipid droplets, dense vesicles with PTH

59

Describe parathyroid oxyphil cells

No known sec role, fxn not known, larger than chief cells, eosinophilic cytoplasm with lots of mitochondria

60

Where are the adrenal glands and what do they look like?

AKA suprarenal glands

Flattened triangular shape

Embedded in perirenal fat at superior poles of kidney

61

What are the 2 parts of the adrenal gland?

Outer cortex (90%)
Inner medulla: cells similar to sump neurons which secrete catecholamines

62

Describe the structure of adrenal gland

Cords of steroid-secreting epithelial cells, separated by parallel sinusoids

63

What are the 3 zones of adrenal cortex and what does each produce?

From outside in:

1. Zona glomerulosa (mineralocorticoids (ie aldosterone))
2. Zona fasciculata (glucocorticoids, 80%)
3. Zona reticularis (gonadocorticoids, androgenic steroids)

Poorly defined zones

64

Describe zona glomerulosa

-15%
-Produces aldosterone
-Closely pack clusters and columns of cells
-Darkly stained nuclei
-Adrenal cortex

65

Describe zona fasciculata

-80%
-Secrete glucocorticoids
-Large, arranged in long straight cords 1-2 cells thick separated by capillaries
-Small nuclei
-Numerous lipid droplets which contain fats, FAs, cholesterol, phospholipids (ie steroid hormone precursors)
-Adrenal cortex

66

Describe zona reticularis

-5-7%
-Make dehydroepi-androsterone (DHEA) and some cortisol
-Smaller than cells of fasciculata
-Few lipid droplets
-Adrenal cortex

67

What is the most common adrenal tumor?

Adrenocortical adenoma

68

What is the adrenal medulla composed of?

Chromaffin cells arranged in groups or cords clustered around capillaries and venules

Modified neurons innervated by presympathetic sympathetic nerve fibers

Considered post-synaptic neurons which lack axons due to cortisol inhibition of chromaffin axonal growth. Cortisol also induces enzymes which convert norepi to epi

69

How do chromaffin products enter blood?

Fenestrated capillaries, numerous secretory vesicles

70

What are the 2 types of chromaffin cells?

Large dense core vesicles (secrete norepi)
Small less dense core vesicles (secrete epi)

71

What is pheochromocytoma?

Tumor of adrenal medulla that secretes epi//norpei

72

What is the pancreas?

An abdominal/retroperitoneal organ with both exocrine/endocrine fxn

73

What is exocrine panc made of

Acini and ducts that produce enzymes used in digestion (most of pancreas)

74

What is endocrine panc made of

Islands of neuroendocrine cells (islets)

75

What is the struc of islet cells

Nets/cords or endocrine cells scattered within panc

1-2% of panc volume

76

Where are islet cells most numerous?

Panc tail

77

When do islet cells dev gestationally

9-12wks

78

Each islet is made up of...

Several cell types:

Major
A
B (70%)
D (somatostatin)

Minor
PP
D-1
EC

79

What histologic features do endocrine organs share?

Vascularity, fenestrated capillaries, nested architecture