histology: endocrine organs Flashcards
How does the endocrine secrete it’s secretion
Directly into the vascular system
What is the type of blood vessels in the endocrine system
Fenestrated or sinusoidal
What endocrine gland does not have fenestrated blood vesels
Testes
What is the effects of the endocrine system
Stimulatory or inhibitory
What system works closely with the endocrine system
Nervous system
What does the nervous system use to communicate
Neurotransmitters that are released locally & bind to receptor on target cell
What does the endocrine system use to communicate
Hormones that circulate & bind to receptor on target cell
What are the two types of hormones
- Lipid soluble: binds to receptors in target cells (diffuse into cell)
- Water soluble: bind to receptor on exterior surface of target cells (cascade of events)
What is the speed of communication of the nervous system vs the endocrine system
Nervous system: rapid communication
Endocrine system: delayed communication
What is the two feedback loops
- Physiological response
- Endocrine axis
What is the two parts of the pituitary gland & origins
- Neurohypophysis from hypothalamus
- Adenohypophysis from roof of mouth
What is another name for pituitary gland
Hypophysis
How does the pituitary form
- Neurohypophyseal bud projects downwards while roof of mouth projects upwards
- Roof of mouth forms the Rathke’s pouch that connect with neurohypophyseal bud
- Roof of mouth loses connection & pituitary is formed
What is the hypothalamohypophyseal portal system
The blood vessels of the anterior pituitary
What regulates secretions of the anterior pituitary
- Neurosecretory cells in hypothalamus
- Negative feedback loops
What is the capillary system of the hypothalamohypophyseal portal system
Fenestrated capillaries
What is the benefit of the hypothalamohypophyseal portal system
System bypasses the heart meaning quicker transport & higher hormone concentration
What connects the anterior & posterior pituitary
Pars intermedia
What is three disorders of the pituitary gland
- Adenoma: under/over production of hormones
- Somatotrophs adenoma: secrete excess GH causing gigantism & acromegaly
- Prolactinomas: deficiency of GnRH leading to infertility
What three tissues are the anterior pituitary composed of
- Cords of epithelial cells
- Minimal supporting connective tissue stroma
- Fenestrated capillaries/sinusoids
What is the two cell types of the anterior pituitary
- Chromophobes: resist stain & undifferentiated chromophils
- Chromophils: important cells
What is the two types of chromophils
- Acidophils
- Basophils
What is the two acidophils cells & what do they secreted
- Somatotrophs: secrete human growth factor hormone/somatotropin
- Lactotrophs: secrete prolactin
What is the three basophil cells & what do they secreted
- Gonadotrophs: secrete FSH & LH
- Thyrotrophs: secrete thyroid stimulating hormone/thyrotropin
- Corticotrophs: secrete ACTH/corticotropin
What is the root of communication in the posterior pituitary
Hypothalamohypophyseal tract
What is another name for the posterior pituitary
Neurohypophysis
What is the function of the posterior pituitary
Store & release two hormones
What is the three cell types in the posterior pituitary
- Pituicytes
- Axons
- Fenestrated capillaries
What is the function of pituicytes
Forms cytoplasmic extensions that inhibits the release of hormones
If stimulated allow for retracting of cell processes & hormones gets exocytosed into pericapillary space
What is mostly secreted by the paraventricular nucleus & supraoptic nucleus
PVN: oxytocin
SON: vasopressin/ADH
What is the structure of the thyroid gland
Two lobes connected with isthmus (band of thyroids tissue)
Surrounded by connective tissue capsule
What is the structural & functional units of thyroid gland
Follicles
What is the three component of the thyroid follicles
- Colloid
- Follicular epithelium cells
- C cells
What is the cell type of follicular epithelium cells
Cuboidal/squamous & becomes columnar when activated
What is the exocrine phase of the thyroid follicles
- TSH binds to receptors
- Iodide pump through the cell trapping iodine at the colloid regions
- Synthesis & glycosylation of thyroglobulin by the rough ER & Golgi apparatus forming a vesicle
- Incorporation of iodine into tyrosyl residue of thyroglobulin by thyroid peroxidase
- Exocytosis of iodothyroglobulin vesicle into colloid region
What is the function of the C cells
Calcium regulation
How does the C cells regulate calcium levels
Increased calcium levels activated C cells to secrete calcitonin that binds to the surface of the activated osteoclasts leading to the ruffled border to disappear & osteoclasts becomes inactivated
What is the two disorders of the thyroid gland
- Hypothyroidism: Hashimoto’s thyroiditis where acini is destroyed
- Hyperthyroidism: Graves disease where acini becomes hyperplastic
What is the two cells in the parathyroid gland
- Chief/principle cells
- Oxyphil cells
What is the function of the chief/principle cells
Calcium sensing receptors for when calcium is low it stimulates secretion of PTH that leads to bone resorption & uriniferous tubules to reabsorb calcium & vitamin D production
What does chief/principle cells contain
Glycogen & secretory granules with parathyroid hormone
What is the three parts of the adrenal cortex
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
What is the cell types, secretion & function of the Zona glomerulosa
Cell type: glomerulus like arrangement
Secretion: aldosterone
Function: helps regulate sodium & potassium homeostasis
What is the cell types,
& secretion of the Zona fasciculata
Cell type: cuboidal cells
Secretion: cortisol
What is the cell types & secretion of the Zona reticularis
Cell type: anastomosing network of short cellular cords
Secretion: androgens
What layer of the adrenal cortex has the most lipid droplets
Zona fasciculata
What is four characteristics of steroid cells
- Polyhedral shaped cells
- Lipid droplets (store cholesterol)
- Prominent smooth ER
- Mitochondria tubular cristae
What is the three cell type in adrenal medulla
- Amine secreting cells
- Numerous nerve fibres
- Vascular plexus
How is catecholamines released from the adrenal medulla
- Tyrosine gets converted into DOPA, dopamine then norepinephrine in a chromaffin cell & stored in a granule
- Cortisol comes from the cortex to the medulla & activates PNMT
- PNMT cleaves norepinephrine into epinephrine
- Epinephrine re-enters the granule & stored
- Ach is released in fight or flight response & transported to adrenal gland via axon of pre-ganglionic sympathetic neuron
- Ach causes a release of calcium & triggers epinephrine release into the bloodvessel
What is the blood supply of the adrenal gland
Adrenal artery
1. Capsular artery
2. Subcapsular plexus
3. Cortical & medullary arteries
What is the vein supply of the adrenal artery
Central medullary vein thick bundles of smooth, longitudinal muscles
What is two disorders of the adrenal gland
- Cushing syndrome: excess cortisol
- Pheochromocytoma: excess adrenaline
What is the two functions of the pancreas
- Endocrine
- Exocrine
What is the exocrine function of the pancreas
Secretion of digestive enzymes into GIT via ducts
What is the four cell types of the endocrine pancreas & secretion
- A cells: glucagon
- B cells: insulin
- D cells: somatostatin & gastrin
- PP/F cells: inhibits somatostatin secretion
What is glucagons function
Induce hepatic glycogenolysis
What is insulin function
Cellular uptake of glucose
What is somatostatin & gastrin
Inhibits glucagon & insulin release
What is the endocrine & exocrine blood supply of the pancreas
Insulo-acinar portal system
What is the exocrine blood supply of the pancreas
Acinar vascular system
What is the three regulatory mechanisms of Islet cells
- Vascular communication
- Cell-cell communication
- Neural communication
What is six effects of menopause
- Vasomotor disturbance: fall in core temperature followed by fells of heat & perspiration
- Atrophy of vaginal epithelium
- Decrease vaginal secretion
- Decrease circulation to vagina & uterus
- Pelvic relaxation: loss of vaginal tone
- Risk of vascular disease, osteoporosis & Alzheimer’s increase
What is four sources of extragonadol estrogen & effects
- Adipose tissue decrease osteoporosis risk
- Bone tissue
- Blood vessels ensure vascular health
- Brain aids memory & cognitive function
What is the endocrine phase of the thyroid follicles
- Colloid droplets are enveloped by apical pseudopods & endocytosis from colloid containing vesicle
- Intracellular colloid droplets fuses with lysosome
- Lysosomal enzymes degrade iodothyroglobulin to release T3 & T4
- T3 & T4 are lipids soluble & diffuse into blood
