Chapter 13 - Endocrine system Flashcards Preview

Histology second semester > Chapter 13 - Endocrine system > Flashcards

Flashcards in Chapter 13 - Endocrine system Deck (117):
0

Endocrine system consists:

- Of ductless glands
- Endocrine cells, isolated in the epithelial lining of the digestive tract and in the respiratory system
- Richly vascularized so that the hormones easily can enter the blood stream

1

Endocrine system

- Regulates metabolic activities in certain organs and tissues of the body, thereby helping to bring about homeostasis
- Produces slow and diffused effect via hormones, whoch are released into the blood stream to influence target cells at remote site

2

Endocrine glands are:

- Pineal body
- Pituitary gland
- Thyroid gland
- Parathyroid glands
- Suprarenal glands

3

Endocrine glands are ductless, while the exocrine glands

Empty their secretions in a duct system and exert only local effect

4

Hormones

Chemical messngers that are produced by endocrine glands and deliverd by the blood stream to target cells or organs

5

Most homones elicit several effects on their target cells:

- Short-term effects
- Long-term effects

6

Hormones are classified into 3 types based on their composition:

1. Proteins and polypeptides
2. Amino-acid derivates
3. Steroid and fatty acid derivates

7

Proteins and polypeptides

- Mostly water-soluble
- E.g:
> Insulin
> Glucagon
> Follicle-stimulating hormone (FSH)

8

Amino-acid derivates

- Mostly water-soluble
- E.g:
> Thyroxine
> Epinephrine

9

Steroid and fatty acid derivates

- Mostly lipid-soluble
> Progesterone
> Estradiol
> Testosterone

10

Hormone receptors

- The hormons binds on specific receptors on (or in) the target cell.
- The binding of a hormone to its receptor communicates a message to the target cell innitiatingsignal transduction, or translation of the signal into biochemical reaction.

11

Where does the thyroid and steroid hormons binds to on the cell?

They bind to the cytoplasmicsurface

12

Second messengers:

- Cyclic guanosine 3',5'-monophosphate (cGMP)
- Metabolites of phosphatidylinositol
- Caclium ions
- Sodium ions (in neurons)

13

Which receptors use G proteins to activate a second messenger, which elicites a metabolic response?

Receptors for:
> Epinephrine
> Thyroid-stimulating hormone (TSH)
> Serotonin

14

Which hormones use catalytic receptors taht activate protein kinase to phosphorylate target proteins?

- Insulin
- Growth hormone

15

Positive feedback mechanism

Travels to the endocrine gland, and initiates an increase in hormone secretion

16

Feedback mechanism

Regulation of the endocrine glands maintains homeostasis

17

What happens with the hormone when they reach their target cells?

They become permanently inactivated in their target tissue; additionally they may be degraded and destroyed in the liver and kidneys

18

Pituitary gland, or hypophysis.

- Endocrine glad
- Composed of portions derived from the oral ectoderm and from neuronal ectoderm
- Produces hormones that regulates growth, metabolism, and reproduction

19

Subdivions of the pituitary gland:

1. Adenohypophysis
2. Neurohypophysis

20

Adenohypophysis

Develops from an rvagination of the oral ectoderm (Rathke's pouch) that lines the primitive oral cavity (stomadeum)

21

Neurohypophysis

Develops from neural ectoderm as a downgrowth of the diencephalon

22

The cellular constituens and the function of the adenohypophysis and neurohypophysis is

Different, because of the different embryological origin

23

Location of the pituitary gland

- Below the hypothalamus
- Sits in the hypophyseal fossa, a bony depression in the sella turcica of the sphenoid bone that is lined by the dura mater, called diaphragma sellae

24

What controls the secretion of nearly all of the hormones produced by the pituitary?

Hypothalamus

25

Subdivision of the pituitary gland, hypophysis:

- Adenohypophysis
> Pars distalis (pars anterior)
> Pars intermedia
> Pars tuberalis
- Neurohypophysis
> Median eminence
> Infundibulum
> Pars nervosa

26

Blood supply of the pituitary gland

- The hypophyseal poratl system of veins delivers neurosecretory hormones from the primary capillary plexus of the median eminence to the secondary capillary plexus of the pars distalis
- The arterial supply is provided from two pairs of vessles that arise from the internal carotid artery

27

Superior hypophyseal arteries

(Pituitary gladnd)
- Supply the pars tuberalis and the infundibulum
- Form a capillary network, the primary capillary plexus, in the median eminence

28

Inferior hypophyseal arteries

(Pituitary gland)
- Primarly supply the posterior lobe
- Send a few branches to the anterior lobe

29

Hypophyseal portal veins

(Pituitary gland)
- Drain the primary plexus of the median eminence, which delivers it blood into the secondary capillary plexus, located in pars distalis

30

Primary capillary plexus and Secondary capillary plexus

- Both are fenestrated

31

Hypothalamic neurosecretory hormones
(Pituitary gland)

- Manufactured in the hypothalamus
- Stored in the median eminence
- Enter the primary capillary plexus
- Drained by the hypophyseal portal veins
- Course: goes through the infundibulum and connect to the secondary capillary plexus in the anterior lobe. Here the neurosecretory hormones leave the blood to stimulate or to inhibit the parenchymal cells

32

From where does the anterior lobe develop from?

Rathke's pouch

33

Rathke's pouch

A diverticulum of the oral ectoderm

34

What does the adenohypophysis consist of?

It consist of pars distalis, pars intermedia, and the pars tuberalis

35

What does the parenchymal cells of the pars distalis consis of?

- Chromophils
- Chromophobes

36

What is another word for the anterior lobe of the pituitary gland?

Pars distalis

37

What is the anterior lobe of the pituitary gland composed of?

cords of parenchymal cells that are surrounded by reticular fibers
> these fibers are surrounded by large sinusoids of the secondary plexuses

38

How is the endothelial lining of the sinusoid in the pars distlis, anterior lobe of the pituitary gland?

it is fenestrated

39

Chromophils

Parenchymal cells of the pars distalis that have an affinity for dyes are called chromophils

40

Chromophobes

Parenchymal cells of the pars distalis that have not an affinity for dyes are called chromophobes

41

Chromophils subdivision?

Acidophils and basophils

42

What types of cell are the acidophils and the basophils?

They are chromophils

43

Where are the acidophils and the basophils?

They are in the pars distalis, or the anterior lobe of the pituitary gland

44

Somatotophs

- Acidophil
- Secrete: somatotrophin (growth hormone)
- Stimulated by: SRH
- Inhibited by: Somatostatin

45

Mammotrophs

- Release: prolactin
> Estrogen and progesteron inhibit prolactin
> The release of prolactin is stimulted by Prolactin-releasing Factor (PRH) and oxytocin

46

What stimulates the release of prolactin from mammotrophs?

The release of prolactin is stimulted by:
- Prolactin-releasing Factor (PRH)
- Oxytocin

47

Granules of basophils:

- Cortitrophs
- Thyrotrophs
- Gonadotrophs

48

Where are basophils ususally located?

at th periphery of the pars distalis, or the anterior lobe of the pituitary gland

49

The corticotrophs

- Secrete: Adrenocorticotropic hormone (ACTH) and lipotropic hormone (LPH)
> The secretion is stimulated by CRH

50

Adrenocorticotropic hormone (ACTH)

Stimulates cells of the suprarenal cortex to release their secretory products

51

Thyrotrophs

- Embedded in the cords of the parenchymal cells at a distance from the sinusoids.
- Have secretory granules containing thyrotropin (TSH)
- Secretion is stimulated by: TRH
- Secretion is inhibited by: T4 and T3 in the blood

52

Gonadotrophs

- Situated near the sinuses
- Secrete FSH and LH
- Secretion is stimulated by LHRH
- Secretion is inhoboted by various hormones that are produced by ovaries and testes

53

Who have less cytoplasm:
a. Chromophobes
b. Chromophils

Answer: a. Chromophobes.
Chromophobes generally have less cytoplasm than the chromophils

54

Chromophobes

Represent either nonspecific stem cells or partly degranulated chromophils

56

Folliculostellate cells

- Nonsecretory cells
- Unknown function
- Location: pars distalis
- Form gap junction with other folliculostellate cells

57

Where does the pars intermedia lie?

the pars intermedia lies between the pars distalis and the pars nervos

58

What contains cysts that are remants of Rathke´s pouch?

pars intermedia of adenohypophysis

59

Rathke´s cyst?

- cuboidal, cell-lined, containing cyst
- remants of the ectoderm of the evaginating Rathke´s pouch

60

The pineal gland is

responsive to diurnal light and dark periods and is thought to inluence gonadal activity

61

Pineal gland =

pineal body

62

What type of gland is the pineal gland (pineal body)?

endocrine gland

63

What influence the secretion of the pineal gland (pineal body)?

the light and dark periods of the day

64

Where is the pineal gland (pineal body)?

it is a cone-shaped, midline projection from the roof of the diencephalon, within a recess of the third ventricle extending to the stalk that is attached to it.

65

The pineal gland (pineal body) measurements:

- 5-8 mm long
- 3-5 mm wide
- 120 mg

66

What covers the pineal gland?

the gland is coverd by pia mater, forming a capsule from which septa extend, dividing the pineal gland into incomplete lobules

67

How does blood vessels enter the pineal gland?

blood vessels enter the gland via the connective tissue septa

68

What types of cells are in the pineal gland and what are they composed of

the parenchymal cells of the gland are composed primarily of pinealocytes and interstitial cells

69

Pinealocytes (general definition):

pinealocytes are the parenchymal cells of the pineal gland that are responsible for secreting melatonin

70

Pinealocytes:

- slightly basophilic
- contain synaptic ribbons
- they synthesize melatonin from tryptophan

71

Pinealocytes organelles:

- well developed cytoskeleton, composed of microfilaments, microtubules and synaptic ribbons
- have SER and RER
- numerous of mitochondria

72

Where are synaptic ribbons observed?

- pineal gland (pinealocytes)
- retina
- inner ear

73

When is melanocytes released?

at night

74

Melatonin:

- inhibits the release of growth hormone and gonadotropin y the hypophysis and hypothalamus, respectively

75

Melatonin´s effect on feelings:

it induces the feeling of sleepiness and, therefore, some individuals use it as a supplement to combat sleep disorders, mood disorders, and depression.

76

Interstitial cells (general def.):

interstitial cells of the pineal gland are believed astroglia-like/astrocyte-like cells

77

Where are corpora arenacea found?

(=brain sand) pineal gland

78

Corpora arenacea =

brain sand

79

Corpora arenacea (brain sand)

- concreations of calcium phosphates and carbonates, which are deposited in concentric rings around an organic matrix
- appear in early childhood and increase in size with age

80

What innervates the pineal body?

postganglionic sympathetic nerves from the superior cervical region. as the axon enters the gland the myelin is lost and they synapse on the pinealocytes

81

Norepinephrine:

norepineprine, released at the pinealocytes, controls production of melatonin

82

What controls production of melatonin?

norepineprine, released at the pinealocytes, controls production of melatonin

83

Which glands absence would be incompatible with life? and why

The absence of parathyroid gland is incompatible with life because parathyroid hormone (PTH) regulates the blood calcium levels

84

How many parathyroid glands do most people have?

4

85

Where is the parathyroid gland located?

on the posterior surface of the thyroid gland

86

Is the parathyroid gland enveloped?

yes. each parathyroid gland is enveloped in its own, thin, collagenous connective tissue capsule

87

What does PTH act on? and why?

- bone
- kidneys
- intestines (indirectly)

* to maintain the optimal concentrations of calcium within blood and interstitial tissue fluid

88

What does the parathyroid gland develop from?

the parathyroid gland develop from the third (becomes inferior parathyroid glands. they descend with thymus) and fourth (becomes superior parathyroid glands) pharyngeal pouches during embryogenesis

89

What does the parenchyma of the parathyroid gland consist of?

- chief cells
- oxyphil cells
- intermediate cells

90

Parathyroid gland measurements:

- 5 mm in length
- 4 mm wide
- 2 mm thick
- 25-50 mg

91

What does the septa of the parathyroid gland serve as?

the septa serve mainly to support the parenchyma and consist of cords or clusters of epithelial cells surrounded by reticular fibers, which also support the parenchyma and a rich capillary network

92

What does the connective tissue stroma of the parathyroid gland in older adults contain?

it can contain up to 60% adipose tissue

93

What does chief cells synthesize?

parathyroid hormone (PTH)

94

Parathyroid hormone manufacturing:

- its precusor, preproparathyroid hormone, is synthesized on ribosomes of the RER and rapidly cleaved as it is transported to the lumen of the RER to form proparathyroid hormone

95

Oxyphil cells (general def.):

are believed to be the inactive phase of chief cells

96

Where does the PTH bind?

PTH binds to the receptors on the osteoblast, signaling the cells to increase their secretion of osteoclast-stimulating factor = increasing bone resorption

97

What does the PTH controls when it comes to the gastrointestinal tract?

PTH controls the rate of calcium uptake in the gastrointestinal tract by indirectly regulating the production of vitamin D in the kidneys; vitamin D is necessary for intestinal uptake of calcium

98

Suprarenal (adrenal) gland (general def.):

suprarenal gland produce two different groups of hormone; steroids and catecholamines

99

Where are the suprarenal glands located?

- located at the superior poles of the kidneys and are embedded in adipose tissue
- they are retroperitoneal, located behind the peritoneum, and surrounded by connective tissue capsule that contains large amounts of adipose tissue

100

Which suprarenal gland is pyramid-shaped and sits on top of the kidney?

the right suprarenal gland

101

Which suprarenal gland is more crescent-shaped and lies along the medial border of the kidney?

the left suprarenal gland

102

Does the suprarenal cortex and medulla have the same origin?

Nope.
- the suprarenal cortex arises from mesoderm
- the suprarenal medulla arises from the neutral crest

103

What does the suprarenal cortex produce?

- hormone called corticosteroids (cortisol and corticosterone), which are synthesized from cholesterol. The corticosteroids are regulated by ACTH

104

What secretes ACTH?

the anterior pituitary gland

105

What does the suprarenal medulla produce?

- epinephrine
- norepinephrine

106

Blood supply to the suprarenal gland is provided by:

arteries from three separate sources:
* inferior phrenic arteries
* aorta, from which the middle suprarenal arteries originate
* renal arteries

107

what forms the subcapsular plexus?

- inferior phrenic arteries
- aorta, from which the middle suprarenal arteries originate
- renal arteries

108

Where does the superior renal arteries originate?

inferior phrenic arteries

109

Where does the inferior suprarenal arteries originate?

renal arteires

110

Where does the short cortical arteries arise from?

the subcapsular plexus

111

Where can we fins the short cortical arteries and the long cortical arteries?

suprarenal gland

112

Long cortical arteries:

pass unbranched through the cortex and into the medulla, where they form a network of capillaries. Thus the suprarenal medulla recieves dual blood supply:
- an arterial supply from the long cortical arteries
- numerous of vessels from the cortical capillary beds

113

Short cortical arteries:

- form a network of sinusoidal fenestrated endothelial walls

114

How is the suprarenal cortex divided:

the suprarenal cortex is divided into three zones (three classes of adrenocortical hormones) that produce three classes of steroids (without storing them)

115

What are the zones that the suprarenal cortex is divided in to:

- zona glomerulosa
- zona fasciculata
- zona reticularis

116

What are the three classes of adrenocortical hormones:

- mineralocorticoids
- glucocorticoids
- adrogens

*all are synthesized from cholesterol, the major component of low-density lipoprotein

117

What does the zona glomerulosa secrete?

parenchymal cells of the zona glomerulosa, when stimulated by angiotensin II and ACTH, synthesize and release the hormones aldosterone and deoxycorticosterone