L1 endocrine anatomy

Question 1

endocrine glands general structure?

Answer 1

Are ductless and secrete hormones

Question 2

Endocrine response is slower than neuro response because:

Answer 2

Hormones are released from specific cells
Hormones have to diffuse to & cross capillary wall; blood transport is slower than nerves
Relies on diffusion once hormone leaves the vascular system

Question 3

Some chemicals serve as both neurotransmitters and hormones ?

Answer 3

E.g. Adrenaline (epinephrine) and noradrenaline (norepinephrine)
Both of these molecules are produced by the adrenal glands as well as being a neurotransmitter and are part of the sympathetic response (fight or flight)

Question 4

‘Local’ Hormones

Answer 4

Have a local effect, i.e. only travel a short distance to effector tissue
Usually only small amounts are found in the general circulation
e.g. secretin and cholecystokinin
Includes paracrine hormones which don’t enter vasculature to reach their target organ
e.g. gastrin and epidermal growth factor

Question 5

‘General’ hormones

Answer 5

Secreted by specific endocrine glands
Transported around the body in blood
Cause many different reactions
e.g. adrenaline (epinephrine) and noradrenaline (norepinephrine) secreted from adrenal medulla
Some hormones have general and local effects
e.g. testosterone secreted from Leydig cells
Some hormones have very set target tissues with specific receptors
e.g. ACTH from anterior pituitary causes release of adrenocortical hormones from the adrenal cortex

Question 6

List 4 types of hormones based on chemistry

Answer 6

1. Steroid hormones
2. Protein hormones
3. Tyrosine hormones
4. Fatty acid hormones(eicosanoids)

Question 7

Carrier molecules

Answer 7

Hormones may circulate freely or be bound to carrier molecules
Free hormones degrade quickly while bound ones last longer
Carrier molecules usually proteins

Question 8

Steroid hormones

Answer 8

hormones that structure related to cholesterol
Cells vacuolated, lots lipid, mitochondria, SER
Cortisol, aldosterone, oestrogen, progesterone, testosterone

Question 9

Protein hormones

Answer 9

Proteins, polypeptides, amino acid hormones
Cells dense staining with secretory granules
Lots mitochondria, RER, ribosomes
ADH, oxytocin, insulin, glucagon, parathyroid h.

Question 10

Tyrosine hormones

Answer 10

Catecholamines ( hormones made by adrenal glands), thyroid hormones

Question 11

Endocrine organs are classically characteristised by >

Answer 11

an endocrine organ contains tissue which releases hormone directly into the blood

Question 12

Fatty acid hormones (eicosanoids)

Answer 12

Derived from arachadonic acid

Prostaglandins, prostacyclins, leukotrienes & thromboxanes

Question 13

List the organs that are primarily endocrine

Answer 13

Pituitary, pineal, thyroid, parathyroid, adrenals

Question 14

List the organs that combine endocrine Fx with other major functions

Answer 14

Testes, ovary, pancreas, placenta

Question 15

endocrine organs which have relatively incidental endocrine Fx (diffuse endocrine system)

Answer 15

• Kidney, Liver, thymus, heart, GI tract

- Often paracrine rather than endocrine

Question 16

Three types of endocrine organs

Answer 16

Three types

Organs that are primarily endocrine

Combines endocrine function with other major functions

Relatively incidental endocrine function (‘diffuse endocrine system’)

Question 17

Typical Endocrine Gland Characteristics

Answer 17

Scattered throughout body and a range of embryological origins
Secrete hormones from cells that are usually derived from epithelial cell origins
Ductless
Highly vascular
Sparse connective tissue framework

Question 18

Different Morphology of endocrine glands (4)

Answer 18

1. Follicular
2. Cell masses or cords
3. Solitary endocrine cells
4. Neurocrine cells

Question 19

Morphology of endocrine gland Follicular

Answer 19

Thyroid, ovary

• -> Hormones stored in follicle lumen but reabsorbed to enter capillary network
• -> follicular in nature but no ducts

Question 20

Morphology of endocrine glands Cell masses or cords

Answer 20

Pituitary, adrenal cortex, interstitial tissue of testis, JG cells

Question 21

Morphology of endocrine gland solitary endocrine cells

Answer 21

Enteroendocrine cells

Question 22

Morphology of endocrine glands –> neurocrine cells

Answer 22

Typical neurone cells whose products are released into the blood
hypothalamus, pineal

Question 23

Fx of hormones (4)

Answer 23

Reproduction (sex hormones)
Growth and development (TH and GH)
Maintenance of internal environment (adrenals, parathyroid)
Energy production and storage (thyroid and pancreatic hormones)

Essential for life – deficiencies or excess can occur

Question 24

Hyperadrenocorticism

Answer 24

Cushings disease

Question 25

List all the areas where endocrine tissue is found

Answer 25

``` Parathyroid Thyroid pineal hypothalamus pituitary thymus stomach intestine testis placenta uterus ovary kidney adrenal ```

Question 26

Endocrine organs of the head region

Answer 26

Question 27

Hypothalamus

Answer 27

At base diencephalon on floor of 3rd ventricle Immediately above the pituitary gland ‘Master gland’ as it controls the release of many of other hormones from pituitary Integrates endocrine & CNS Neurosecretory neurons extend down into pituitary Hormones are all small polypeptides

Question 28

2 routes of horse release by the hypothalamus

Answer 28

1. Neurosecretory cells | 2. Hormones released

Question 29

Neurosecretory cells pathway of the hypothalamus

Answer 29

manufacture and transport their hormones via their axons to the posterior pituitary (neurohypophysis) in neurosecretory granules Hormones stored in disteneded ends of axons (Herring bodies) until secretion 2 hormones released: antidiuretic hormone (ADH or vasopressin; SO nuc.) Oxytocin (PV nuc.)

Question 30

Other neurosecretory cells in the hypothalamus

Answer 30

Other neurosecretory cells in the hypothalamus release hormones into the hypothalamic-pituitary portal vessels that travel to the anterior pituitary (adenohypophysis) cause release or inhibition of the trophic hormones of the anterior pituitary

Question 31

Hypothalamic hormones that use the hypothalamus-pituitary portal system include:

Answer 31

Corticotrophin releasing hormone/factor (CRH/F) Growth hormone release-inhibiting hormone (GHRIH/ somatostatin/ somatotrophin release inhibiting factor) Prolactin release-inhibiting hormone (PRIH or dopamine) Thyroid releasing hormone (TRH) Gonadotropin releasing hormone/ factor (GnRH)

Question 32

B. Pituitary (Hypophysis) --? Consists of 2 regions of different tissue type

Answer 32

``` Anterior pituitary (adeno-hypohysis) composed of: Pars distalis (P. anterior) Pars intermedia Pars tuberalis ``` Posterior pituitary (neuro-hypophysis) composed of: Pars nervosa (P. posterior) Infundibulum Median eminence

Question 33

Embryology of the pituitary

Answer 33

Question 34

Diaphragm sellae =

Answer 34

horizontal fold of dura, forms roof of sella turcica

Question 35

Median eminence Infundibulum Sella turcica

Answer 35

Median eminence = stalk with 3rd ventricle Infundibulum = pituitary stalk Sella turcica = small depression in basisphenoid

Question 36

Hormones of the pituitary

Answer 36

``` Anterior pituitary Adrenocorticotrophic h. (ACTH) Thyroid stimulating h. (TSH) Gonadotrophic hh. Follicle stimulating h. (FSH) Luteinising h. (LH) Growth h./ somatotrophic h. (GH/ STH) Prolactin α-melanocyte stimulating h. (MSH; from pars intermedia) ``` Posterior pituitary Oxytocin Antidiuretic h. (ADH)/ vasopressin

Question 37

Histology of the pituitary gland

Answer 37

Question 38

Histo - andenohypophysis

Answer 38

Cords of cells & sinusoidal capillaries ``` Cells classed dye affinity Chromophils (A & B) Active, lots secretory granules Somatotrophs 45% Mammotrophs 20% Corticotrophs 20% Thyrotrophs 5% Gonadotrophs 5% ``` Chromophobes (C) Resting?

Question 39

Answer 39

Question 40

Hsiotology of the hypophysis (cont) --> pars Intermedia (of adenohypophysis)

Answer 40

Question 41

Histology of hypophysis Neurophyopophysis

Answer 41

Question 42

Cone of Wulzen

Answer 42

=outpocket of pars intermedia that looks more like adenohypophysis in OX

Question 43

Pineal Gland = Epiphysis

Answer 43

Small, darkly pigmented outgrowth from dorsum 3rd ventricle Sits between cerebral hemispheres & cerebellum Foci of calcification ‘brain sand’ in advanced age Main hormone is melatonin

Question 44

Functions of the Pineal gland

Answer 44

Regulates diurnal and circadian rhythms Light → retina → hypothalamus → sympathetic fibres → pineal ↑ daylight → ↓ melatonin Melatonin secreted into blood or CSF of 3rd ventricle Alters secretion of gonadotrophic hormones by anterior pituitary Long day breeders e.g. horse ↑ daylight → ↓ melatonin → ↑ ovarian function Short day breeders e.g. goat ↓ daylight → ↑melatonin → ↑ ovarian function

Question 45

Other functions of the pineal gland

Answer 45

2. Inhibits puberty Antigonadotophic effects Relatively active prepubescent animals 3. Regulates daily fluctuations of corticosteroids Circadian clock in suprachiasmic nucleus 4. Photoreceptor in lower vertebrate Regulates colour change

Question 46

Histology of pineal gland

Answer 46

S – brain sand P – pinealocytes (pineal chief cells) N – neuroglial cells