Endocrine Anatomy Flashcards
Recap:
State the functions of the endocrine system
- communicate and regulate in response to normal physiologic changes in the body
- communicate and regulate in response to alterations in external environment to ensure body’s homeostasis
State the 3 locations of endocrine cells
- endocrine glands - pituitary, thyroid, parathyroid, adrenal, pineal (MELATONIN)
- cluster of cells in organs- pancreatic islets, thymus, kidney, ovarian follicles, corpus luteum
- single cells/isolated cells in epithelia - endocrine cells of gut, neuroendocrine or amine precursor uptake and decarboxylation (APUD) cells
State some examples of endocrine glands
- pituitary gland
- thyroid gland
- parathyroid gland
- adrenal gland
- pineal gland
State some examples of clusters of cells in organs that are endocrine cells
- pancreatic islets
- thymus
- kidney
- ovarian follicles
- corpus luteum
State some examples of single/isolated cells in epithelia which are endocrine cells
- endocrine cells of gut
- neuroendocrine cells
- amine precursor uptake and decarboxylation (APUD) cells
State the 4 types of hormones
hormone is a biologically active substance released and transported in the bloodstream
1. peptide/protein
2. steroids
3. tyrosine or amine-derived
4. fatty acid derivative
ENDOCRINE GLAND
- Contains ____ and ____ epithelium for ____ cells
- Cells arranged in ____
- Contains ____ connective tissue to act as supportive framework
- ____ blood supply with ____ capillaries to support large pool of hormones secreted at each time + efficient uptake of hormones into bloodstream
- ____ of ducts
ENDOCRINE GLAND
- Contains CUBOIDAL and COLUMNAR epithelium for SECRETORY cells
- Cells arranged in CORDS
- Contains MINIMAL connective tissue to act as supportive framework
- RICH blood supply with FENESTRATED capillaries to support large pool of hormones secreted at each time + efficient uptake of hormones into bloodstream
- ABSENCE of ducts
State 4 adaptations of endocrine glands
- rich blood supply with fenestrated capillaries –> supports large pool of hormones secreted at one time + efficient uptake of hormones into bloodstream
- contains minimal connective tissue –> acts as supportive framework
- contains cuboidal and columnar epithelium for secretory cells + arranged in cords
- absence of ducts
State the anatomical location of pituitary gland
hypophyseal/pituitary fossa attached to under surface of brain/hypothalamus by stalk
State the hormones secreted by the pars distalis
- GH
- ACTH
- TSH
- PL
- FSH
- LH
State the embryological derivation of anterior and posterior pituitary gland
ANTERIOR PITUITARY = outpouching of the roof of pharynx (rathke’s pouch)
POSTERIOR PITUITARY =extension of diencephalon
PITUITARY GLAND
Anatomical location:
Function:
Embryological derivation:
PITUITARY GLAND
Anatomical location: hypophyseal/pituitary fossa attached to under surface of brain/hypothalamus by stalk
Function: secretion of hormones (MSH, TSH, ACTH, LH, FSH, PL, GH)
Embryological derivation: ANTERIOR PIT develops from outpouching of roof of pharynx (rathke’s pouch), POSTERIOR PIT develops from extension of diencephalon
State the 2 differences between anterior and posterior pituitary gland
DIFFERENCE 1: type of cells/tissues
- Anterior pit = secretory cells for hormones (esp pars distalis)
- Posterior pit = nervous tissue
DIFFERENCE 2: embryology
- Anterior pit = outpouching of pharynx (rathke’s pouch)
- Posterior pit = extension of diencephalon
State the vessel supplying blood to pituitary gland
internal carotid artery branches
- primary capillary plexus (superior hypophyseal arteries) (FOR STALK AND MEDIAN EMINENCE)
- inferior hypophyseal arteries (FOR POSTERIOR PIT)
- hypophyseal portal veins
- hypophyseal veins
- secondary capillary plexus (FOR ANTERIOR PIT)
State the 3 parts of the anterior pituitary gland and their functions.
(1) PARS DISTALIS - secretion of hormones
(2) PARS INTERMEDIA - part between the anterior and posterior pituitary
(3) PARS TUBERALIS - part of pituitary that clamps on fundle/stalk
PARS DISTALIS
- Function =
- 2 types of cells:
- State whether the 2 cells can be differentiated by staining
PARS DISTALIS
- Function = responsible for secretion of hormones
- 2 types of cells: CHROMOPHILS and CHROMOPHOBES
- The 2 cells canot be differentiated by staining
(A) CHROMOPHILS
- Function = secretory cells where hormones are stored in cytoplasmic granules
- Have a darker stain
- Consists of acidophils and basophils
- Acidophils secrete GH (somatotrophs) and PL (mammotrophs)
- Basophils secrete FSH + LH (gonadotrophs), ACTH + corticotropin (corticotrophs), TH (thyrotrophs)
(B) CHROMOPHOBES
- Are degranulated chromophil cells
- Have a lighter stain
State the types of cells in PARS INTERMEDIA and PARS TUBERALIS
PARS INTERMEDIA - melanotrophs (melanocyte stimulating hormones)
PARS TUBERALIS - gonadotrophs (undifferentiated), chromophobes and some acidophils and basophils
Explain how the hypothalamic hypophyseal portal system works to regulate production of hormones at the adenohypophysis.
HYPOTHALAMIC HYPOPHYSEAL PORTAL SYSTEM:
hormones from the hypothalamic nuclei (TRH, GnRH, CRH, GHRH) are transported to the anterior pituitary via the primary and secondary capillary plexus to control the production of hormones at the anterior pituitary
State the 3 structures that make up the neurohypophysis
- axons of neurosecretory cells in supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus
- pituicytes (supporting cells)
- herring bodies (neural secretory bodies)
State the hypothalamic hormones stored in herring bodies.
Recap the location of herring bodies
Hormones in herring bodies:
1. ADH - acts on renal tubules to reduce urinary flow by increasing water absorption
2. Oxytocin - induces uterine contraction during labour and milk expulsion from mammary glands
Herring bodies are located on the neurohypophysis
Explain the processes involved in the hypothalamic hypophyseal tract.
HYPOTHALAMIC HYPOPHYSEAL TRACT
- OH and ADH are secreted and produced from the hypothalamus and are transported to the neurohypophysis via axons
- Hormones enter the bloodstream through the posterior pituitary to be transported to the target organs
THYROID GLAND:
Anatomical location:
Function:
Embryological derivation:
THYROID GLAND:
Anatomical location: anterior and inferior to the larynx in region of neck, 2 lobes connected by isthmus + has capsule surrounding it. It is lined by the pretracheal fascia at the posterior surface
Function: Production of thyroid hormone (TH)
Embryological derivation: From foregut endoderm near base of developing tongue
Name the blood vessels which supply the thyroid gland.
- superior thyroid artery
- inferior thyroid artery
- thyroid ima artery (less important)
State the nerves that accompany each artery that supplies the thyroid gland.
Explain any complications related to the above.
Superior thyroid artery is accompanied by branch of vagus nerve –> ligation leads to vocal cord palsy
Inferior thyroid artery is accompanied by recurrent laryngeal nerve –> compression causes hoarseness of voice
State a unqiue feature of thyroid gland which differs from that of other endocrine glands.
Thyroid gland is the only endocrine gland that stores its secretions in a large amount in the follicular lumen in the centre.
All other endocrine glands store secretions within itself.
State the microscopic features and the cell types in a thyroid gland.
THYROID GLAND
Microscopic: Rounded epithelial follicles
Cells:
1. Follicular cels - cuboidal (non-active), tall columnar (active)
2. Colloid centre containing thyroglobulin
3. Parafollicular cells - c cells of thyroid
State the functions and features of follicular and parafollicular cells.
FOLLICULAR CELLS
- Function = contains tri-iodothyronin (T3) and thyroxine (T4) which regulate BMR and influnce growth and maturation of nervous tissues
- Features = cuboidal (non-active), tall columnar (active)
PARAFOLLICULAR CELLS
- Function = secretes calcitonin which regulate blood calcium level
- Features = larger than follicular cells, stain less intensely
Explain how thyroid hormones (TH) are synthesised.
- Thyroglobulin is synthesised and discharged by SER into the follicle lumen
- Inactive iodide from the capillary is trapped in the thyroid follicle cell and oxidised into active form of iodine
- Iodine enters the follicle lumen and gets attached to tyrosine in colloid to form DIT (T2) and MIT (T1)
- Iodinated tyrosine link together to form T3 and T4
- Thyroglobulin colloid is endocytosed and combines with lysosome
- Lyosomal enzymes cleave T4 and T3 from thyroglobulin colloid and hormones diffuse from the follicle cell into the bloodstream to be transported to peripheral tissues
Explain how regulation of T3 and T4 levels occur.
TRH (thyrotropin releasing hormone) released by hypothalamus stimulates release of TSH (by pituitary gland) which stimulates release T3 and T4
PARATHYROID GLAND
Anatomical location:
Function:
Embryological derivation:
PARATHYROID GLAND
Anatomical location: 4 ovoid masses lying on posterior surface of thyroid gland within capsule
Function: secretes PTH (parathyroid hormone) which helps to raise blood calcium levels
Embryological derivation: third and fourth pharyngeal pouches
State the types of cells in parathyroid gland. State the function and features of each cell.
PARATHYROID GLAND
(1) Chief cells
- Function = active cells that produce PTH
- Feature = small polyglonal cells with round nuclei and pale staining cytopasm
(2) Oxyphil cells
- Function = inactive cells
- Feature = large cells that are more acidophillic and more staining
Recap: State the types of cells found in
1. Adenohypophysis
2. Neurohypophysis
3. Thyroid gland
4. Parathyroid gland
ADENOHYPOPHYSIS
- Pars distalis - chromophils (acidophils, basophils) + chromophobes
- Pars intermedia - melanotrophs
- Pars tuberalis - gonadotrophs, chromophobes, acidophils, basophils
NEUROHYPOPHYSIS
- Axons of neurosecretory cells in supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus
- Pituicytes
- Herring bodies
THYROID GLAND
- Follicular cells
- Parafollicular cells
- Colloid centres containing thyroglobulin
PARATHYROID GLAND
- Chief cells
- Oxyphil cells
Explain PTH secreted by chief cells regulate calcium levels.
- Low serum calcium levels stimulate chief cells to secrete PTH
- PTH stimulates increased osteoclastic activity in bones to release calcium into blood
- PTH directlhy increases calcium reabsorption in DCT of renal cortex and inhibits phosphate reabsorption in PCT
- PTH indirectly increases calcium absorption in small intestine by stimulating vitamin D absorption
- PTH hence increases calcium levels back to homeostatic levels
State some functions of calcium (7)
- muscle contraction
- nerve conduction
- blood coagulation
- activation of enzymes
- second messenger
- myocardial function
- bone and teeth formation
Explain the pathophysiology of hyperparathyroidism leading to hypercalcaemia.
- Hyperparathyroidism results in increased PTH secretion from overactive parathyroid gland
- Increased PTH signals increased action by osteoclast to breakdown bone tissue
- Increased PTH signals reduced calcium excretion and increases calcium reabsorption in DCT of renal cortex (inhibits phosphate reabsorption in PCT)
- Increased PTH signals indirect increased calcium absorption in the gut by stimulating vitamin D absorption
State any association of hypoparathyroidism and hyperparathyroidism.
HYPOPARATHYROIDISM –> after total thyroidectomy (hypocalcaemia)
HYPERPARATHYROIDISM –> tumours (adenomas), chronic renal failure
ADRENAL GLAND
- Anatomical location:
- Function:
- Embryological derivation:
ADRENAL GLAND
- Anatomical location: superior poles of kidneys
- Function: maintain the constancy of the internal environment of the body and make appropriate physiological changes in response to acute stress
- Embryological derivation: mesoderm (adrenal cortex), neural crest (adrenal medulla)
State the types of cells located in the adrenal cortex and adrenal medulla
ADRENAL CORTEX
- Steroid secreting cells that have acidophilic cytoplasm rich in lipid droplets with central nuclei
ADRENAL MEDULLA
- Chromaffin cells - large pale staining polyhedral cells lined in cords or clumps
- Ganglion cells
- Epinephrine and Norepinephrine produced
ADRENAL CORTEX
- ____ secreting cells that have ____ cytoplasm rich in ____ droplets with ____ nuclei
- Steroids are not stored in ____ and will diffuse through the plasma membrane directly
- Have abundant ____ and ____ that have enzymes for ____ synthesis
ADRENAL CORTEX
- STEROID secreting cells that have ACIDOPHILIC cytoplasm rich in LIPID droplets with CENTRAL nuclei
- Steroids are not stored in GRANULES and will diffuse through the plasma membrane directly
- Have abundant SER and MITOCHONDRIA that have enzymes for CHOLESTEROL synthesis
State the 3 parts of the adrenal cortex and state what each part primarily contains.
- zona glomerulosa - mineralcorticoids
- zona fasciculata - glucocorticoids and adrenal androgens
- zona reticularis - glucocorticoids and androgens
ADRENAL MEDULLA
- Contains ____ cells = large pale staining ____ cells lined in ____ or ____
- Contain electron dense granules containing ____
- Cells are innervated by ____ sympathetic neurons that trigger the release of ____ and ____
ADRENAL MEDULLA
- Contains CHROMAFFIN cells = large pale staining POLYHEDRAL cells lined in CORDS or CLUMPS
- Contain electron dense granules containing CATECHOLAMINES
- Cells are innervated by PREGANGLIONIC sympathetic neurons that trigger the release of EPINEPHRINE and NOREPINEPHRINE
State what conditions are associated with
1. hypoadrenalism
2. hyperadrenalism
HYPOADRENALISM - adrenal cortical insufficiency/ addison’s disease
HYPERADRENALISM - adrenal cortical tumours
- excess glucocorticoids (cortisol) = hypercortisolism = cushing’s syndrome
- excess mineralcorticoids (aldosterone) = hyperaldosteronism = conn’s syndrome
PANCREAS (islets of langerhans)
- Anatomical location
- Microscopic features
PANCREAS (islets of langerhans)
- Anatomical location: inner curvature of the 2nd-3rd part of the duodenum
- Microscopic features:
(1) Compact spherical/ovoid masses of endocrine cells embedded within the acinar cells - More darkly stained
(2) More rounded/polyglonal, smaller endocrine cells - More lightly stained
- Islets acidophilic/basophilic with cytoplasmic granules
- Arranged in cords separated by fenestrated capillaries
State the 4 types of cells located in islets of langerhans and the hormones secreted by each cell.
- Alpha cell (20%) - glucagon
- Beta cell (70%) - insulin
- Delta cell (5-10%) - somatostatin
- PP/ F cell (1-2%) - pancreatic polypeptide
State the functions of
1. glucagon
2. insulin
3. somatostatin
4. pancreatic polypeptide
glucagon - increase blood glucose content
insulin - promotes decrease of blood glucose content
somatostatin - inhibits release of other islet cell hormones, inhibits GH and TSH from anterior pituitary and HCL secretion from gastric parietal cells
pancreatic polypeptide - stimulates action of gastric chief cells, decreases bile secretion and pancreatic secretion, decreases bicarbonate secretion, decreases intestinal motility
