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Endo > Endocrine embryology and anatomy > Flashcards

Endocrine embryology and anatomy Flashcards

1
Q

Describe the process of a Sandwich ELISA

A
  • Immobilise antibody being tested on a solid substrate/plastic well
  • Add substrate, antigen (hormone) will bind
  • Was to remove substances not bound to antibodies
  • Add antibodies that will bind to antigen (hormone) and are already enzyme linked
  • Wash to remove excess, unbound antibodies
  • Add reagent that will change colour in presence of enzymes
  • Measure degree of colour change to assess concentration of antigen (hormone)
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2
Q

Describe the process of radio-immuno assays

A
  • Known concentration of hormone/antigen radiolabelled (iodine) bound by Ab to form Ab-hormone complex
  • Unlablleded hormone being tested for added, competes with labelled hormone
  • Resulting hormone-Ab-complexes precipitated using secondary Ab
  • Radiolabelled measured
  • Compare starting amount of radiolabelled to new level, can determine concentration of unknown hormone
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3
Q

What is the coefficient of variation?

A

SD/mean

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4
Q

What is diagnostic sensitivity?

A

The proportion of true positives correctly identified by a test

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5
Q

What is assay sensitivity?

A

The assay’s ability to detect a low concentration of a given substance in a biological sample. Is usually expressed as a concentration

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6
Q

What are the advantages of disadvantages of RIAs?

A
  • Cheap per sample
  • But expire quickly
  • Use of radioisotopes so not suitable for use in veterinary practice
  • Good sensitivity
  • But high coefficient of variation
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7
Q

What are the advantages and disadvantages of ELISA?

A
  • Does not require radioisotopes
  • Good sensitivity (not as good as RIA)
  • Low CV
  • More expensive
  • Easier to do in practice
  • Less kit wastage (do not expire as quickly as RIAs)
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8
Q

What are typical capillary features for endocrine organs?

A
  • Fenestrated epithelium
  • Obvious transcytosis
  • No pericyte
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9
Q

Describe pericytes

A
  • Cells crucial to blood-brain barrier
  • Rounded nucleus vs crescent nucleus of endothelial cells
  • Endothelial cells and pericytes share basement memrbanes
  • Important in control of molecular transport between blood and CNS
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10
Q

List the glands that are entirely endocrine in function

A
  • Hypophysis (pituitary)
  • Pineal
  • Thyroids
  • Parathyroids
  • Adrenals
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11
Q

List the glands that are partly endocrine in function

A
  • Pacreas
  • GIT
  • Kidneys
  • Testes
  • Ovaries
  • Placenta
  • Thymus
  • Heart
  • Adipose
  • Liver
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12
Q

Outline the embryological development of the brain

A
  • Changes in cell shape and number lead to folding
  • Neural plate invaginates along axis = neural groove
  • Neural folds on each side fuse dorsally = tube
  • Neural tube = tissues of CNS (brain rostrally, spinal cord caudally)
  • Neuroepithelial cells bipotential = neurons or supporting neuroglial cells
  • Closure of tube progresses antero-posteriorly
  • Once closed, meninges and vertebral structures develop around it
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13
Q

Outline the development of the ganglia, cranial and spinal nerves

A
  • Some neuroextodermal cells from lateral edges of neural plate not incoporated into tube
  • Persist as neural crest dorsal to neural tube
  • Separate into right and left columns
  • Lots of potential for migration
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14
Q

What is the embryological origin of the pituitary gland?

A
  • Adenohypophysis from roof of mouth

- Neurohypophysis from hypothalamus

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15
Q

What is the origin of the pineal gland?

A

CNS

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16
Q

What is the origin of the thyroid glands?

A

Floor of mouth

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17
Q

What is the origin of parathyroid glands?

A

Pharyngeal arches

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18
Q

What is the origin of the adrenal glands?

A
  • Medulla from neuroectoderm

- Cortex from medoderm (mesonephros)

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19
Q

Describe the embryology of the adenohypophysis

A
  • Upgrowth of ectodermof roof of developing mouth - Rathke’s pouch
  • Buds off, hole in middle becomes left, migrates towards growing brain
  • Cups around developing neurohypophysis
  • Connection with mouth lost
  • Differentiation to glandular tissue
  • Initially round, flattened as comes into contact with the neurohypophysis
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20
Q

What is the consequence of Rathke’s pouch failing to differentiate into glandular tissue?

A
  • Pituitary cysts instead of adenohypophysis
  • Leads to pituitary dwarfism
  • Otherwise are completely neurally competent
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21
Q

Outline GnRH cell migration

A
  • Start in olfactory bulb

- Migrate to hypothalamus

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22
Q

Outline the embryology of the neurohypophysis

A
  • Downgrowth of ectoderm of forebrain (diencephalong/future hypothalamus)
  • Retains connection with brain via infundibulum
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23
Q

What are the 2 holes in the pituitary and where do they come from?

A
  • Recess of third ventricle, dragged down by neurohypophysis
  • Hypophyseal cleft from space in Rathke’s pouch
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24
Q

What are the structures of the diencephalon

A
  • Epithalamus (incl pineal gland)
  • Thalamus
  • Hypothalamus
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25
Q

Where is the pituitary gland located?

A
  • Hanging off the hypothalamus
  • Within “dent” of skull in basisphenoid bone - sella turcica/hypophyseal fossa
  • Dura forms diphragma sellae through while hypophyseal stalk conencts between hypothalamus and hypophysis
  • Outside the BBB, no subarachnoid space in fossa
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26
Q

What are teh rostral, caudal, lateral and ventral relations of the hypophysis?

A
  • Rostrally: optic chiasma
  • Caudally: mammillary bodies
  • Laterally: cavernous sinus
  • Ventrally: sphenoid bone
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27
Q

Where are the venous sinuses and what is their function?

A
  • Either side of base of skull

- Venous drainage from nasal chambers

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28
Q

What are the regions of the adenohypophysis?

A
  • Pars tuberalis
  • Pars distalis
  • Pars intermedia
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29
Q

What is the function of the pars tuberalis of the adenohypophysis?

A

Monitors melatonin levels from pineal gland

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30
Q

Where is the pars intermedia in the adenohypophysis in equidae and carnivores?

A

Surrounds the neurohypophysis

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31
Q

Briefly outline the function of the pars distalis of the adenohypophysis

A
  • Main secretory regions
  • Different cells secreting different hormones
  • Hormonally linked to hypothalamus via capillary portal system
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32
Q

Describe the structure of the neurohypophysis

A
  • Infundibulum attached to tuber cinereum of hypothalamus
  • Neural lobe
  • Outpouching of brain, physically connected by nerve fibres (cell bodies in hypothalamus)
  • Ends of axons (telodendria) from hypothalamus in neurohypophysis
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33
Q

What hormones are secreted by the neurhypophysis?

A
  • Oxytocin

- ADH

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34
Q

Describe the structure of the pars intermedia

A
  • Small area of tissue between 2 main parts of hypophysis
  • Remnants of Rathke’s pouch
  • Poduces MSH in foetus
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35
Q

Describe the location of the pineal gland

A
  • Aka epithalamus/epiphysis
  • Caudo-dorsal part of diencephalon
  • Between tenecephalic hemispheres, cerebellum, and rostral colliculi
  • i.e. small gland on back of thalamus
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36
Q

What is the function of the pineal gland?

A
  • Controls diurnal rhythms
  • Controls breeding seasons
  • Secretes melatonin
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37
Q

Describe the parietal eye in reptiles

A
  • Direct connection to pineal throguh hole in skull

- Sensitive to light, similar to eye

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38
Q

How are the functions of the pineal gland and the pars tuberalis linked?

A

Tuberalis receives melatonin from pineal gland and releases hormones in response

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39
Q

What are the 2 cell types found in the thyroid glands

A
  • Follicular cells

- Parafollicular cells/C-cells

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40
Q

Describe the development of the follicular cells of the thyroid glands

A
  • Downgrowth from pharyngeal endoderm of developing tongue
  • At site of future foramen caecum
  • Starts in middle of tongue, buds down
  • Branches into Y shape
  • Each arm will become left or right lobe
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41
Q

Describe the development of the parafollicular/ C-cells

A
  • Dragged down with follicular cells
  • Originate from ultimobranchial body
  • Endoderm os most caudal pharyngeal pouch
  • May also be of neural crest origin
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42
Q

What is the consequence of the embryology of the thyroid gland?

A

2 cells types not functionally linked present

43
Q

What structeres are formed from the 1st pharyngeal pouches?

A

Eustachian tube, tympanic cavity

44
Q

What structures are formed from the 2nd pharyngeal pouches?

A

Palatine tonsils

45
Q

What structures are formed from the 3rd pharyngeal pouches?

A
  • External parathyroids (III)

- Thymus

46
Q

What structures are formed from the 4th pharyngeal pouches?

A
  • Internal parathyroids (IV)

- C cells in thyroid

47
Q

Describe the development of the parathyroids

A
  • Develop from 3rd and 4th pharyngeal pouches
  • Association with thymus leads to variable species location of external
  • Parathyroid IV inside thyroid in most mammals
  • As thyroid moves down, traps parathyroids but the tissues stay distinct throughout
48
Q

Outline the development of the adrenal cortex

A
  • From mesoderm between gonadal ridge and mesentery

- Cranial end of mesonephros

49
Q

Outline the development of the adrenal medulla

A

From neural cres cells that produce sympathetic gandlia

50
Q

Describe the foetal adrenal cortex

A
  • Develops first
  • Is distinct from adult cortex
  • Produces corticosteroids in all species
  • Converts placental progesterones to androgens to go back to placenta
  • Regresses after birth, replaced by adult cortex
51
Q

Outline the development of the pancreas

A
  • Develops as outgrowth of foregut (dorsal and ventral)
  • Langerhans islets bud off from developing exocrine pancreas
  • Made up of glandular tissue from gut, connective tissue from mesenchyme
52
Q

Describe the location of the thyroid gland

A
  • Around cranial part of trachea

- Just caudal to larynx

53
Q

What structures are found medially to the thyroid gland?

A
  • Trachea
  • Thyroid artery
  • Recurrent laryngeal artery
54
Q

What structures are found dorsally to the thyroid gland?

A
  • Oesophagus
  • Parathyroids
  • Carotid sheath
55
Q

Why might a thyroidectomy not remove all thyroid tissue?

A

Some thyroid tissue dotted all the way down and found in the lwoer neck and thorax in 60% of dogs

56
Q

Describe the connection between the left and right thyroid gland lobes

A
  • Some spcies have functional tissue
  • Others joined by connective tissue
  • Connective region called isthmus
57
Q

What is the function of the follicular cells of the thyroid glands?

A

Production of thyroid hormones T3 and T4, storeed extracellularly

58
Q

Describe the parafollicular cells of the thyroid glands

A
  • Produce calcitonin

- Diffusely spread within gland

59
Q

Describe the histological ppearance of the thyroid glands

A
  • Large pockets of colloid surrounded by follicular cells
  • Colloid is storage protein with thyroid hormones attached
  • Parafollicular cells spread around gland
60
Q

What is the function of the colloid in the thyroid gland?

A
  • Extracellular storage of thyroid hormones

- Means there is no need for constant production and secretion of hormones from cells

61
Q

What species have a functional isthmus in the thyroid gland?

A
  • Pigs
  • Humans
  • Catte
62
Q

What species have a connective tissue connection between the lobes of the thyroid glands?

A
  • Dogs
  • Cats
  • Small ruminants
  • Horses
63
Q

Describe the thyroid gland of horses

A
  • Connective tissue isthmus (non-functional)
  • Very mbile gland
  • Commonly changes size
64
Q

Describe the appearance of teh porcine thyroid gland

A
  • Arrowhead shaped
  • Not very lobular appearance
  • Very small “left” and “right”
65
Q

Describe the appearance of the boxine thyroid gland

A
  • Bumpy
  • Connected by functional isthmus
  • Lobes obvious and round
66
Q

Describe the appearance of the canine thyroid glands

A
  • Smooth
  • Connective tissue isthmus
  • Elongated lobes (oval rather than round)
67
Q

Describe the appearance of the equine thyroid glands

A
  • Connective tissue isthmus
  • Round lobes
  • Smooth
68
Q

What is the cell type of the parathyroid glands?

A

Chief/principle cells

69
Q

Describe the location of the parathyroids in the dog and cat

A
  • IV deep in thyroid
  • Exact position of III is variable
  • Cranial lobes (dogs) or caudal lobes (cats)
  • Often embedded under capsule and difficult to distinguish
70
Q

Describe the parathyroid gland locations of ruminants

A
  • External parathyroid close to bifurcation of common carotid artery
  • Internal associated with thyroid gland
71
Q

Describe the parathyroid gland locations in horses

A
  • External near trachea ~15cm cranial of thoracic aperture, but very variable
  • Internal around cranial part of thyroid or inside it
72
Q

Describe the location of the adrenal glands

A
  • Medial to cranial pole of kidney
  • Some species variations
  • Embedded in a little fat
73
Q

What structures lie close to the adrenal glands?

A
  • Kidneys
  • Caudal vena cava (right adrenal)
  • Aorta (left adrenal)
  • Renal artery and vein
74
Q

What are the layers of the adrenal cortex?

A
  • Zona glomerulosa (outer)
  • Zona fasciculata (middle)
  • Zona reticularis (inner)
75
Q

What is produced by the zona glomerularis of the adrenal cortex?

A

Mineralocorticoids

76
Q

What is produced by the zona fasciculata of the adrenal cortex?

A

Glucocorticoids (and some androgens)

77
Q

What is produced by the zona reticularis of the adrenal cortex?

A

Oestrogens, testosterone, some progesterone (and some glucocorticoids)

78
Q

Describe the adrenal medulla

A
  • Modified nercous tissue

- Arenal and noradrenaline procude here

79
Q

Describe teh innervation of the adrenal medulla

A
  • Innervated by preganglionic sympathetic fibres
  • Post-ganglionic cells have no axons
  • Release NT direclty from cell bodies
80
Q

Describe the endocrine tissue of the pancreas

A
  • Islets of Langerhans
  • Alpha: glucagon
  • Beta: insulin
  • Delta: somatostatin
81
Q

What is the function of the exocrine pancreas?

A

Production of digestive enzymes

82
Q

Which species have a dorsal pancreatic duct?

A

Dog, horse, ox, pig

83
Q

Which species do not have a ventral (right, main) pancreatic duct?

A

Ox, pig

84
Q

Describe the pancreas in the horse

A

Right and left lobes fused

85
Q

Describe the pancreas of the ox

A

Dorsal lobe fused at end of right, single duct for both “lobes”

86
Q

Describe the pancreas of sheep and goats

A

Fused at end of left lobe, single duct for both lobes

87
Q

Describe the pancrease of the pig

A

Complex pattern of fusion between right and left lobe

88
Q

Outline the endocrine function of the GIT

A
  • Produced by enteroendocrine (epithelial) cells in teh gastrointestinal mucosa
  • ~20 cell types producing different hormones
89
Q

List the gastrointestinal hormones

A
  • Gastrin
  • Secretin
  • Cholecystokinin
  • Serotonin
  • Gastric inhibitory polypeptide
  • Somatostatin
90
Q

Name the avian endocrine glands

A
  • Hypophysis (similar to mammals)
  • Pineal gland
  • Pancreas
  • Thyroids
  • Parathyroids
  • Ultimobranchial bodies
91
Q

Describe the endocrine features of the pancreas

A
  • 3 different types of islets
  • Dark islets (alpha cells)
  • Light islets (beta cells)
  • Mixed islets
92
Q

Describe the structure thyroid and parathyroid glands of birds

A
  • Not all physically bound together
  • All located at thoracic aperture
  • Craniolateral to syrinx
93
Q

How is the blood supply to the thyroid arranged?

A

Double blood supply and venous drainage

94
Q

Describe the blood supply to the thyroid

A
  • Cranial thyroid artery (from common carotid)
  • Caudal thyroid artery (from brachiocephalic trunk)
  • Anastomose inside thyroid gland
95
Q

Describe the venous drainage of the thyroid gland

A
  • Thyroid veins

- Drain into internal and external jugular vein and brachiocephalic vein

96
Q

Describe teh innervation of the thyroid gland

A
  • Complete autonomic nerve supply, vasomotor only
  • Sympathetic fibres from cranial cervical ganglion
  • Parasympathetic fibres leave vagus at distal vagal ganglion
  • Sympathetic and parasympthateic, axons travel together in cranial laryngeal nerve
  • Only control blood supply, not release of hormones from gland
97
Q

Describe the innervation of the parathyroids

A

Same as thyroids

  • Autonomic only
  • SNS: cranial cervical ganglion
  • PSNS: vagus from distal vagal ganglion
  • Travel together in cranial laryngeal nerve
  • Control blood supply, not release of hormones
98
Q

Describe the vascularisation of the parathyroid

A

Blood supply from local vessels

99
Q

Describe the vascularisation of the adrenal glands

A
  • Small arterial branches from neighboruing arteries (aorta, renal, lumbar cranial mesenteric)
  • Enter adrenal, run through cortex
  • Comes in radially, converges in middle, into veins and out
  • Medullary central vein collects blood, drained into caudal vena cava
100
Q

What is the consequence of the vascularisation of the adrenal gland

A
  • Hormones in blood stream reach cortex first without having to go through medulla
  • Medullary products can leave into circulation quickly and into systemic
101
Q

Describe the innervation of the adrenal gland

A
  • Sympathetic supply

- Can be considered sympathetic ganglion with post-ganglionic cells rather than post-ganglionic axons

102
Q

Describe the venous drainage of the pancreas

A

Portal vein to liver

103
Q

Describe the blood supply to the pancreas

A

Pancreatic branches of celiac, superior mesenteric and splenic arteries

Endo (30 decks)

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