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ENI 2 > anatomy and embryology > Flashcards

anatomy and embryology Flashcards

1
Q

list endocrine glands that have entirely endocrine functions

A
  • hypophysis (pituitary)
  • pineal
  • thyroid
  • parathyroid
  • adrenals
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2
Q

list endocrine glands that have partial endocrine functions

A
  • pancrease
  • GIT
  • kidneys
  • testes
  • ovaries
  • placenta
  • thymus
  • heart
  • adipose
  • liver
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3
Q

discuss the developmental origins of the hypophysis

A
  • adenohypophysis comes from the roof of the mouth
  • neurohypophysis comes from the hypothalamus
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4
Q

discuss the developmental origins of the pineal gland

A

from CNS

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5
Q

discuss the developmental origins of the thyroids

A

floor of mouth

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6
Q

discuss the developmental origins of the parathyriods

A

from pharyneal arches

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7
Q

discuss the developmental origins of the adrenals

A
  • medulla from the neuroectoderm
  • cortex from the mesoderm
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8
Q

what is the functiuon of the hypophysis

A
  • major link between the electrical activity in the CNS and the hormonal activity of the body
  • source of many reproductive and metabolic hormones
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9
Q

what are the 2 regions of the hypophysis

A
  • adenohypophysis/anterior pituitary/pars distalis
  • neurohypophysis/posterior pituitary/pars nervosa

hypophysis is slightly larger in females and larger still in pregnancy
relatively smaller in large animals

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10
Q

where is the hypophysis located

A

under the hypothalamus
outside dura mater

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11
Q

discuss where the hypophysis is located in relation to the blood brain barrier

A
  • ventral to the hypothalamus
  • in a bony recess in the basisphenoid (hypophyseal fossa)
  • fenestrated capillaries in parts of the hypothalamus = no blood brain barrier
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12
Q

discuss the anatomical landmarks in relation to the hypophysis

A
  • rostrally: optic chiasma
  • caudally: mammillary bodies
  • laterally: cavernous sinuses
  • ventrally: sphenoid bone
  • dorsally: hypothalamus, thalamus and cerebrum
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13
Q

label

A
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14
Q

discuss the 3 parts of the adenohypophysis

A
  • pars tuberalis: monitors melatonin levels. forms a collar around the stalk
  • pars intermedia: minor function in mammals. surrounds neuropophysis in equidae and carnivores
  • pars distalis: main secretory region. collection of cells, each secrete a different hormone
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15
Q

which of these regions is the pars distalis, pars intermedia and neuropophysis

A
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16
Q

what are the 2 regions of the neuropophysis

A
  • infundibulum: the stalk attached to the tuber cinereum of the hypothalamus
  • neural lobe: contains projections axons from neurons in the hypothalamus
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17
Q

the adenohypophysis is __________ linked to the hypothalamus

A

the adenophypophysis is hormonally linked to the hypothalamus
- via a capillary portal system
- releasing factors from the hypothalamus
- histologically variant cells refelct the variety of hormones produced

`

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18
Q

the neurohypophysis is _______________ linked to the hypothalamus

A

the neurohypophysis is neurologically linked to the hypothalamus
- cell bodies in the hypothalamus
- axons extend down the stalk
- end of axons (telodendria) in the neurohypophysis

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19
Q

discuss the embryological development of the adenohypophysis

A
  • upgrowth of ectoderm of roof of developing mouth
  • cups around developing neurophypophysis
  • connects with mouth lost
20
Q

discuss the embryological development of the neurohypophysis

A
  • downgrowth of ectoderm of forebrain (diencephalon/future hypothalamus)
  • retains connection with brain (infundibulum)
21
Q

discuss vascular supply of the hypophysis

A
  • sits within the circle of willis
  • arteries supply the whole brain
  • blood supplied to the hypothalamus. venous drainage enters another capillary network within the hypophysis
  • blood then drains into the cavernous sinuses within the base of the skull around the circle of willis
22
Q

discuss the role of blood supply in cummunication of the hypophysis

A
  • the various releasing hormones are released into the interstitial tissues of the hypothlamus and hypophysis
  • the capillaries are of the fenestrated type to allow free flow of molecules into circulation
  • lack of tight junctions
  • therefore the blood brain barrier is absent from these parts of the hypothalamus and hypophysis
  • allows transport of hormones from hypothalamus to the hypophysis via the blood and then hormones from the hypophysis into the blood
23
Q

discuss how the action of the adenohypophysis is controlled

A
  • releasing factors produced within hypothalamus by specific cells (each produces on type of RF)
  • circulate via the hypothalamo-hypophyseal portal system to the adenohypophysis
  • specific target cells release stimulating hormones
  • again there is a cell tuype for each stimulating hormone
  • stimulating hormones circulate to the target organs and trigger endocrine secretion
24
Q

discuss how the action of the neurohypophysis is controlled

A
  • axons from supraoptic and paraventricular nuclei in hypothalamus from supraoptichypophyseal and paraventriculohypophyseal tracts
  • descend va the infundibulum to the neural lobe
  • terminations of axons release antidiuretic hormone and oxytocin
25
Q

what does the pineal gland do

A
  • controls circadian rhythms
  • controls breeding seasons
  • can also mediate courtship/breeding behaviours
  • linked with seasonal hair/feather colour changes
  • modulates existing processes rather than initiates them
26
Q

in what species will you not find a pineal gland

A
  • crocodiles
  • dugongs
  • armadillos, sloths and anteaters
27
Q

describe where the pineal gland is located in comparison to other structures

A
  • caudal dorsal part of the diencephalon
  • located between the telencephalic hemispheres, cerebellum and rostral colliculi
28
Q

does the pineal gland have a BBB

A
  • no BBB
  • very high blood flow
  • very cellular
29
Q

discuss the role of the pineal gland in melatonin production

A
  • modulates sleep patterns
  • important in annual breeders like sheep and horses
  • less light = more melatonis
  • inhibits reproductive cycles in long day breeders
  • stimulates reporoductive cycles in short day breeders
  • melatonin levels are monitored by the pars tuberalis to coordinate reproductive hormone periodicity/seasonality by affecting the release of LH and FSH
30
Q

what are the 2 secretory elements of the thyroid gland

A

follicular cells
- thyroid hormone T3 and T4 (metabolic effects)
- store is extracellular
- form a football of cells around the store of the hormone (thyroglobulin)

parafollicular or C cells
- calcitonin (lowers blood calcium)
- diffusely spread within the gland

31
Q

T3 and T4 are bound to what protein

A

TG protein

32
Q

what process releases T3 and T4 from TG protein

A

proteolysis

33
Q

describe where the thyroid is located

A
  • around cranial part of trachea
  • left and right glands may be joined by an isthmus
  • medially, trachea, thyroid aa., recurrent laryngeal nerve
  • ventrolaterally stenohyoid muscle and veins
  • dorsally esophagus, parathyroids, carotid sheath and contents
34
Q

describe the appearance of the thyroid gland histologically

A

follicular cells make a football effect containing TG, which binds thyroid hormones stores extracellularly

35
Q

discuss the species differences of the thyroid

A
  • pigs, cattle have functional isthmus
  • dogs, cats, small ruminants and horses have seperate L and R glands
  • you may find fibrous isthmus connecting L and R glands
  • thyroid is very mobile in horses
36
Q

discuss embryological development of the thyroid

A
  • follicular cells are a down-growth from pharyngeal endoderm of developing tongue at site of future foramen caecum
  • parafollicular or C cells get collects as thyroid is pushed down
37
Q

discuss the vascular supply of the thryoid

A
  • cranial thyroid artery (common carotid) and caudal thyroid artery (brachiocephalic trunk)
  • thyroid vein will drain into external jugular and brachiocephalic veins
38
Q

discuss the nervous supply to the thyroid

A
  • has a complete autonomic supply that is vasmotor only
  • sympathetic fibres come from the cranial cervical ganglion
  • parasympathetic fibres leave the vagus at the distal vagal ganglion
  • the S and PS axons travel together in the cranial laryngeal nerve
39
Q

how many parathyroid glands are there and where are they located

A

internal and external glands on each thyroid (2 pairs)
- external usually seen on outside sitting on cranial pole (dogs) or caudal pole (cats)
- internal inside or next to (but CR inside)
- 2-3 mm diameter nodule

40
Q

label

A
41
Q

discuss blood and nerve supply to the parathyroids

A
  • nerve same as thyroid
  • blood supply fro local vessels depending on location (reason why it is possible to transplant)
42
Q

discuss the location of the adrenals

A

medial to cranial pole of the kidney

43
Q

label

A
44
Q

what does the cortex of the adrenal glands produce by zone

A

GFR:
zona glomerulosa = mineralcorticoids
zona fasciculata = glucocorticoids
zona reticularis = androgens

45
Q

what does the medulla of the adrenal gland produce

A

catecholamines

46
Q

discuss the embryological development of the adrenal glands

A
  • cortex from mesoderm between gonadal ridge and mesentery
  • medulla from neural crest cells that produce the sympathetic ganglia
  • cortical cells are produced by stem cells near the surface and migrate centrally (remnants become zona intermedia)
  • medullary cells are still migrating into the gland at birth so can be found in extra-cortical sites
  • random aggregations of cortex can be found in the abdomen of older animals
  • in the fetus the cortex produces GC in order to initiate partuition
  • relatively large in the fetus and regresses after birth as the adult cortex developes
47
Q

discuss venous supply to the adrenal

A
  • small arterial branches from neighbouring arteries
  • branches from aorta, renal, lumbar and cranial mesenteric arteries
  • enter the adrenal and split into: supply to cortex and supply to medulla

drainage:
- draining the cortex enters the medullary sinusoids
- mixes with blood draining the medullary cells
- central medullary veins collect the blood, which is drained into the caudal vena cava

ENI 2 (81 decks)

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