- Hypophysis; thyroid; parathyroid; adrenal

- Kidneys; ovaries/testis; placenta - Have both endocrine and exocrine function

L3 - Nuts and bolts of the endocrine system Flashcards by yeswanth AKULA

What are hormones

Mediator molecules

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What are hormones essential for

Normal growth and development
adaptation to internal and external environment
contribute to the process of sexual reproduction

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Features of nervous system

• Nervous system via neural impulse transmission
Mediator molecules => Neurotransmitters
Very fast (1-2ms)
Act locally from pre to post synapse (microns)

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Features of endocrine system

• Endocrine system via the release of hormones
Mediator molecules => Hormones
Much slower (seconds/minutes/days)
Act anywhere in the body via the circulatory system
• Each hormone elicits a response from any cell carrying a receptor sensitive for that hormone

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Properties of endocrine glands

Ductless
Hormone is released to interstitial space –> blood stream or lymphatic system
Highly vascularised

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What determines how hormones affect other cells metabolism

number of molecules available
number of receptors available
affinity hormone-receptor

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Chemical classification of hormones

Steroid (oestradiol; testosterone)
Protein/peptide (ADH; oxytocin; insulin)
Amine(adrenalin; noradrenalin; dopamine)
NO (nitric oxide) is both neurotransmitter and hormone

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What are the germ layers

Ectoderm
Mesoderm
Endoderm

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Discrete glands

Hypophysis; thyroid; parathyroid; adrenal

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Larger glands

Kidneys; ovaries/testis; placenta

- Have both endocrine and exocrine function

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What is the diffuse neuroendocrine system

Scattered nerve cells with endocrine function

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What is the hypophysis

Compound gland suspended from the hypothalamus by stalk or infundibulum

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Where is the hypophysis located

Sella turcica (turkish saddle), sphenoid bone

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Function of pituitary gland

Master endocrine gland

- Produces several hormones that influence activity of other endocrine glands(eg liver)

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What is adenohypophysis

Glandular part
Outpouching of ectoderm of oral cavity
Rathke’s pouch
FSH, LH; TSH, etc

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Divisions of hypophysis

Adenohypophysis

- Neurohypophysis

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What is neurohypophysis

Neural part

- Downgrowth from diencephalon of brain (oxytocin; ADH)

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Blood supply to the hypophysis

Superior hypophyseal
Inferior hypophyseal
Branches of int carotid

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What does the superior hypophyseal supply

Median eminence

- Upper part of stalk

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What does the inferior hypophyseal supply

Neurohypophysis

- Lower part of stalk

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What do arteries supplying median eminence and stalk end as

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Capillary plexuses

What are capillary plexuses in median eminence and stalk ending drained by

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Portal veins

Where do the portal veins in the hypophysis pass to

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Pass to anterior lobe of pituitary
Veins then form a secondary capillary plexus
This setup provides a route for neurosecretory substances released from the hypothalamus to also reach the anterior lobe

What causes release of hormones from adenohypophysis and neurohypophysis

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Signals from the hypothalamus

What are the two lateral lobes of the thyroid gland connected by

- By an isthmus that courses anterior to the trachea

Location of the thyroid gland

- From just below oblique line of thyroid cartilage to 5/6 tracheal ring; immediately anterior to trachea

What is the thyroid gland derived from

- Derived from endoderm, develops as a growth from floor of pharynx, near base of tongue

What is the thyroid gland regulated by

· Under control from hypothalamus (thyrotropin-releasing hormone) and hypophysis (thyroid stim hormone) · Essential role in regulating tissue metabolism, growth and development

Blood supply to the thyroid gland

- Superior thyroid (from external carotid) | - Inferior thyroid (from subclavian)

Blood drainage of thyroid gland

- From an extensive plexus into the internal jugular vein and brachiocephalic vein

Features of parathyroid glands

· 4 parathyroid glands: 2 superior and 2 inferior; embedded in capsule of thyroid; posterior aspect · Very small, about the size of a grain of rice; 40 mg

What do the parathyroid glands mostly develop from

- Develop mostly from cells originating from 3rd/4th pharyngeal pouches; migrate caudally with the thymus - Inferior parathyroids travel to lie lower compared to superior parathyroids

Role of the parathyroid gland

- Secrete parathyroid hormone

Function of parathyroid hormone

- Regulates calcium and phosphate levels

Why do the parathyroid glands have to be preserved during thyroidectomy

- If removed, blood calcium levels fall --> muscles, inc respiratory and laryngeal, go into tetanic contraction --> death

Parathyroid glands - VAN

Artery - primarily inferior thyroid (also superior) Vein - superior, middle + inferior thyroid Nerve - from middle and inferior cervical ganglions

Location of adrenal glands aka suprarenal glands

- Sup pole of kidneys (T12); retroperitoneal

What is the adrenal cortex derived from

- Mesoderm(mesothelium)

What is the adrenal medulla derived from

- Neural crest cells

What does the adrenal cortex secrete

- Corticosteroids

What do cells subjacent to capsule in the adrenal glands secrete

- Mineralocorticoids eg. aldosterone | - Function to maintain electrolyte balance

What does the deeper part of cortex in the adrenal glands secrete

- Secrete glucocorticoids eg. hydrocortisone | - Affect metabolism and electrolyte balance

What does the cortex also produce

- Adrenal androgens eg testosterone

What do the secretory cells of the medulla develop from

- Chromaffin cells develop from same embryonic tissue as sympathetic ganglia

What do the medulla cells secrete

- Secrete adrenaline and smaller amounts of noradrenaline - i.e catecholamines

Blood supply to the adrenal glands

- Superior (from inferior phrenic) - Middle (from aorta) - Inferior suprarenal arteries (from renal) - Arteries branch before entering capsule and the rami supply the cortex and medulla of gland

What do the cortical arteries give rise to

- Subcapsular plexus and in turn to cortical sinusoids that distributes blood to cortical cells

Venous drainage of adrenal glands

- Drain into IVC (R) | - Renal vein (L)

What is the activity of adrenal glands under control of

- Hypothalamus eg. ACTH release from hypophysis | - Symp division of ANS: coeliac; splanchnic nerve

What does ACTH stimulate the secretion/release of

- Corticosteroids

What is the adrenal medulla under the control of

- Under direct control from ANS (symp) --> fast response

What are adrenal gland secretions initiated by

Impulses from preganglionic sympathetic fibres that end in the chromaffin cells of the medulla Chromaffin cells then release catecholamines into adjacent circulation

L3 - Nuts and bolts of the endocrine system Flashcards

(52 cards)