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ENDO > Embryology and anatomy > Flashcards

Embryology and anatomy Flashcards

1
Q

Which glands have an entirely endocrine function?

A
  • Thyroid
  • Pituitary
  • Pineal
  • Parathyroids
  • Adrenals
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2
Q

What are the medulla and cortex of the adrenal glands formed from?

A

The Medulla is from the neuroectoderm and the cortex is from the mesoderm (mesonephros)

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3
Q

What forms the thyroid and parathyroids?

A

The thyroid is formed from the floor of the mouth.

The parathyroids from the pharyngeal arches

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4
Q

Where is the hypothalamus located?

A

Beneath the thalamus, at the floor of the 3rd ventricle

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5
Q

Describe the hypophysis

A

Link between the CNS and the hormonal activity of the body

Has 2 regions= Adenohypophysis and neurohypophysis

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6
Q

Where is the hypophysis located?

A

Ventral to the hypothalamus

  • It is in a bony recess = hypophyseal fossa. (Sella turcica= the fossa and surrounding processes)
  • Dura forms the diaphragm through which the hypophyseal stalk projects to connect between hypothalamus and hypophysis
  • NO subarachnoid space in the fossa as it needs to be outside the BBB
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7
Q

What are the different regions of the adenophypophysis?

A

Pars tubercularis= monitors melatonin levels and it located around the stalk
Pars intermedia= Surrounds neurohypophysis in equidae and carnivores
Pars Distalis= main secretory region, collection of cells with each secrete a different hormone

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8
Q

What part of the adenohypophysis is absent in horses?

A

The cleft of hypophysis

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9
Q

Describe the anatomy of the neurohypophysis

A
  • Infindubulum= the stalk. It attaches to the tuber cinereum of the hypothalamus (nerves run through it)
  • Neural lobe= contains projections from neurons in the hypothalamus
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10
Q

How is the adenohypophysis linked to the hypothalamus?

A
  • Hormonally
  • Has a capillary portal system
  • Capillaries go down into adenophypophysis where hormones are released into bloodstream.
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11
Q

Describe how the neurohypophysis is linked to the hypothalamus

A
  • Neurologically

- Cell bodies located in the hypothalamus, axons extend down the stalk into the neurophypophysis

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12
Q

Describe the pars intermedia

A
  • Produces MSH in the fetus
  • In ages horses tumours here= PPID: excess production of both MSH and ACTH as they both have the same precursor- pro opiomelanocortin.
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13
Q

What happens in Rathke’s pouch doesn’t differentiate into glandular tissue?

A
  • Adenohypothysis doesn’t develop and instead pituitary cysts develop
  • This is what causes pituitary dwarfism in German shepherds
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14
Q

What causes pituitary dwarfism in German shepherds?

A

The failure of Rathke’s pouch to differentiate into glandular tissue

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15
Q

Describe GnRH cell migration

A

-They start in the olfactory bud-> migrate to the hypothalamus

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16
Q

Describe the development of the neurohypothysis

A
  • Downgrowth of ectoderm of the forebrain

- Retains its connection with the brain via the infindibulum

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17
Q

Describe the capillaries around the hypophysis

A
  • They are fenestrated allowing free flow of molecules (espesh hormones) into the circulation
  • No tight jundctions
  • Results in BBB being absent from these parts of hypothalamus and hypophysis
18
Q

Where are releasing factors produced? Give two examples

A
  • in the hypothalamus
  • CRF= Cortisol releasing factor
  • TRF= Thyroid stimulating hormone
19
Q

Where is the pineal gland located?

A

In the caudo dorsal area of the diencephalon

20
Q

What is the epithalamus?

A

The pineal gland

21
Q

What does the pineal gland control?

A
  • Circadian rhythms
  • Controls breeding season
  • Varies in size between species
22
Q

What does the pineal gland produce and how does it get its information?

A
  • Gets information about day length from visual tracts

- Produces and secretes melatonin

23
Q

What are the affects of melatonin?

A
  • Moderates sleep patterns

- Important in annual breeders ( inhibits/ stimulates repro cycles dependant on whether long or short day breeders)

24
Q

What measures the melatonin levels?

A

Pas tuberalis

25
Q

Where is the thyroid gland located?

A

-Around the cranial part of the trachea

26
Q

Describe the cell of the thyroid gland

A

Follicular cells: Secrete T3 and T4.

Parafollicular (C-cells) secrete calcitonin which lowers blood calcium.

27
Q

What can get confused with the thyroid gland in horses?

A

When a horse is put onto fresh grass the parotid glands can swell up- owners can confuse them for the thyroid gland

28
Q

How does the thyroid of cattle and pigs differ to that of dogs, cats, small ruminants and horses?

A

-Cattle and pigs have a functional isthmus whereas the others have separate left and right glands

29
Q

What is the origin of C cells of the thyroid gland?

A

Neural crest

30
Q

Describe the vasculature of the thyroid

A
  • Cranial thyroid= from common carotid
  • Caudal thyroid= from brachiocephalic trunk
  • The veins drain into the internal/ external jugular veins
31
Q

In ruminants where is the parathyroid located?

A
  • External PT= near bifurcation of common carotid

- Internal PT= associated with the thyroid gland

32
Q

What cells produce PTH?

A

The principal cells

33
Q

Describe the anatomy of the adrenal gland

A 
-Cortex has 3 layers:
Zona glomerularis (outer)-mineralocorticoids (ADH)
Zona fasciulata (middle)-glucocorticoids
Zona reticularis (inner)-androgens
-Medulla = made from modified nervous tissue and is involved in making adrenaline/noradrenaline
34
Q

What are the cortex/ medulla of the adrenal gland made from?

A
  • Cortex= mesoderm -> mesonpephros

- Medulla= neural crest cells

35
Q

Describe the development of the pancreas

A
  • Organ develops as outgrowth of foregut

- Langerhans islets bud off from exocrine pancreas

36
Q

What are the main cell types of the pancreas?

A

Alpha cells= produce glucagon
Beta cells= produce Insulin
Delta cells= produce somatostatin

37
Q

How does venous blood from the pancreas drain?

A

Via the hepatic portal vein into the liver

38
Q

Which species have a fused pancreas and which don’t?

A

Horse, pig, ruminants

39
Q

What is an entero endocrine cell?

A

-Chemosensitive cell in the GIT

40
Q

Describe the pancreas of a bird

A

-3 different types of islets:
Light islets= beta cells
Dark islets= alpha cells
Mixed islets

41
Q

Which thyroid hormone is predominant in birds?

A

T4

ENDO (39 decks)

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