Lecture 1 & 2 Flashcards
Classify endocrine glands based on chemical components of their secretion.
Steroids: gonadal & adenocortical steroids
Small peptides, polypeptide, & proteins: insulin, glucagon, GH, LH, ACTH
Amino acids and Arachiodonic Acid analogs & deriv: catecholamines, PGs, prostacyclin, and leukotrienes (thyroid hormones)
Describe common histological characteristics
of all endocrine glands.
- ductless
- cords of cells invested in reticular fibers
- fenestrated capillaries (may be called sinusoids)
- secrete hormones that act on target organs
Describe the development of the pituitary gland.
anterior lobe:
- evagination of ectoderm of oropharynx
- 3 derivatives of Rathke’s pouch:
1. par distalis: anterior wall of pouch
2. pars intermedia: posterior wall of pouch
3. pars tuberalis: lateral walls of pouch
posterior lobe:
- downgrowth (embryonic infundibulum) of neuroectoderm of the floor of the diencephalon (3rd ventricle)
- 2 parts:
1. pars nervosa
2. infundibulum
Identify & describe the glandular and nervous tissue components of the pituitary gland
Anterior lobe: glandular tissue (Adenohypophysis)
- pars tuberalis
- pars distalis
- pars intermedia
Posterior lobe: neural tissue (Neurohypophysis)
- mediam eminence
- infundibulum
- pars nervosa
State the significance of hypothalamo-hypophyseal portal system.
provides crucial link between the hypothalamus and pituitary gland. System carries the neuroendocrine secretions from their site of release in mediam eminence and infundibulum directly to the cells of the pars distalis.
Identify & describe the microscopic structures of anterior and posterior pituitary.
Anterior pituitary (cellular):
PARS DISTALIS:
- Chromophobes: unknown
- Chromophils:
Acidophils: somatotropes (GH; inhibited by somatostatin) & mammotropes (PRL; inhibited by dopamine)
Basophils:(B-FLAT) gonadotropes (FSH & LH), corticotropes (ACTH), & thyrotropes (TSH)
PARS INTERMEDIA:
- production of alpha-MSH
- colloid filled cystic cavities
- basophilic cuboidal cells
Posterior pituitary (neurohypophysis):
- Herring bodies: release hormones into blood stream
- Pituicytes
- Fenestrated capillaries
-supraoptic nucleus: production of ADH
paraventricular nucleus: production of oxytocin
List the hormones produced by the cells of anterior pituitary and describe the major functions.
FLAT PiG Follicle stimulating hormone (FSH): stimulates follicular development in the ovary and spermatogenesis in the testis Luteinizing hormone (LH): regulates final maturation of ovarian follicle, ovulation, and corpus luteum; in males, essential for maintenance and secretion of adrogen secretion by Leydig cells Adrenocorticotropic hormone (ACTH): maintains structure and stimulates secretion of glucocorticoids and gonadocorticoids by zona fasciculata and zona reticularis of adrenal cortex Thyrotropic hormone (TSH): stimulates growth of thyroid epithelial cells; stimulates production and release of thyroglobulin and thyroid hormones Prolactin (PRL): promotes mammary gland development; initiates milk formation; stimulates and maintains secretion of casein, lactalbumin, lipids, and carbohydrates into milk Growth hormone (GH): stimulates liver and other organs to synthesize and secrete insulin-like growth factor I, which stimulates division of progenitor cells in growth plates and in skeletal muscle
Identify & describe the structure and functions of the pars intermedia.
- surrounds a series of small cystic cavities, colloid-filled follicles (residual Rathke’s pouch)
- basophilic cuboidal cells: production of MSH
- unclear function
Identify & describe the components of posterior pituitary.
PARS NERVOSA:
- contains non-myelinated axons and their nerve endings (neurosecretory neurons); cell bodies lie within supraoptic nuclei and paraventricular nuclei
- axons form hypothalamophyseal tract
INFUNDIBULUM
- connects posterior lobe to hypothalamus
List the hormones that are stored in the posterior pituitary, their origin and their effects.
Oxytocin:
- synthesized in paraventricular nuclei
- acts on uterine contractions and millk release
ADH:
- synthesized in supraoptic nuclei
- increases permeability of renal collecting tubule to water and vasoconstricts
State the significance of pituicytes and Herring bodies.
Pituicyte: only cells specific to posterior lobe of pituitary gland; specialized glial cells containing intermediate filament protein, charateristic of astrocytes
Herring bodies: dilations of unmyelinated axons containing secretory granules
Describe the blood supply to the pituitary gland.
Superior hypophyseal arteries: arises from internal carotid arteries and posterior communicating arteries of circle of Willis; supplies the pars tuberalis, median eminence, and infundibulum
Inferior hypophyseal arteries: arise from internal carotid artieries; supplies pars nervosa
superior hypophyseal arteries –> fenestrated capillaries (primary capillary plexus) –> hypophyseal portal veins –> second fenestrated capillary network –> cavernous sinus at base of diencephalon –> systemic circulation
IMPORTANT:
- direct communication between hypothalamus and posterior pituitary
- communication between anterior pituitary and hypothalamus is via portal system
Describe the anatomical location and blood supply to the adrenal gland.
Located at superior poles of kidneys.
Blood supply: superior, middle, and inferior suprarenal arteries –> branching before entering capsule –> capsular capillaries, fenestrated cortical sinusoidal capillaries, and medullary arterioles –> adrenomedullary collecting veins –> central adrenomedullary vein –> IVC
Identify and describe the cortical zones of adrenal gland, hormones produced there and their function
superficial to deep: (GFR)
Zona Glomerulosa: thin, most superficial layer; globular arrangement
- aldosterone: electrolyte and water balance
Zona Fasciculata: thick, longitudinal columns arrangement
Zona Reticularis: trabeculae-like arrangement
Z. Fas. & Z. Ret. produce cortisol and androgens (DHEA): increase protein, carbohydrate, and fat metabolism and suppress immune function
Identify and describe
the adrenal medulla, hormones produced there and their function.
Chromaffin cells:
- modified post-ganglionic neurons; no axons/dendrites
- secrete catecholamines
Ganglion cells:
- axonal processes extend into cortex and modulate secretion