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Endocrine System - Coggle Diagram
Endocrine System
Pituitary
Location and Anatomy
- in the hyphyseal fossa
- covered by projection of the dura mater
called diaphragm sella
- connected to hypothalamus by
infundibular stalk
Anterior adenohypophysis
General
- derived from primitive oral cavity
- upgrowth of Rathke's pouch
- pars distalis, intermedia, and tuberalis
- produces and releases hormones
Hormones
- ACTH (adrenocorticotropic hormone): stimulates adrenal glands to produce hormones
- FSH (follicle stimulating hormone) and LH (luteinizing hormone): work together for functioning of ovaries and testes
- GH (growth hormone): in children, essential for healthy body composition and growth.
in adults, aids healthy bone and muscle mass and affects fat distribution
- PRL (prolactin): stimulates breast milk production
- TSH (Thyroid stimulating hormone): stimulates the thyroid
Pars
Pars Intermedia (btwn sup and ant)
- separated from distalis by residual
clefts of Rathke's pouch
- cells secrete MSH which stimulates
melanocytes to produce melanin
- function uncertain
Pars Distalis 75%
- endocrine cells, fenestrated
capillaries and CT
-
Cel types Function
Somatotrophs 50%
- somatotropin (GH) stimulates growth in all
of the body and epiphyseal plates
Mammotrophs or lactotrophs 15-20%
- secrete PRL, promotes mammary gland
development during pregnancy and promotes
milk secretion in the lactating mammary gland
Corticotrophs 15-20%
- secretes ACTH, stimulates adrenal cortex and helps
regulate lipid metabolism
Thyrotrophs 5%
- secrete TSH, stimulates thyroid hormone synthesis
storage and release
Gonadotrophs 10%
- secrete FSH and LH
- FSH, growth of ovarian follicles
and estrogen secretion in women and
spermatogenesis in men
- LH, ovulation, conversion of the ruptured follicle
into corpus lute, maintenance of the corpus,
production of testosterone
Pars Tuberalis
- funnel-shaped extension of distalis
around infundibular stalk
- most of cells are gonadotrophs
Control of Secretion
- negative feedback and other hormones
Hypothalamic hormones:
Stimulating
- TRH thyrotropin release hormone
- GnRH Gonadotropin-releasing hormone
- GHRH GH releasing homrone
- CRH corticotropin-releasing hormone
Inhibiting
- dopamine inhibits PRL
- Somatostatin inhibits GH and TSH
-
Hypothalamic-Hypophyseal
Tract
- bundle of axons travels into the neurohypophysis
from the hypothalamic nuclei
- Supraoptic nucleus ADH
- Paraventricular nucleus Oxytocin
- axonal transport and accumulate temporarily
in the icons of the hypothalamic hypophyseal
tract before their release and uptake by capillaries
Portal System
- carries small regulatory peptides from
hypothalamus to anterior pit
- superior hypophyseal arteries --> median eminence
and indfundibular stalk
- inferior hypophyseal arteries --> neurohypophysis
Hormones
- act directly on non-endocrine tissues
(GH, PRL, ADH, OT, MSH)
- modulate other endocrine glands
(TSH, ACTH, FSH, LH)
- secretion directly controlled by the
hypothalamus
Clinical Correlation
Pituitary adenoma, excessive number
of chromophils, gigantism or acromegaly
blidness first symptom
Thyroid
Follicles
- hollow spheres with simple epithelium
resting on a BM
- height of epithelium varies with
level of activity of the gland (controlled
by TSH)
- Active = columnar, Hypoactive = squamous
- center contains gelatinous acidophilic colloid
- contain pink colloid
- surrounded by follicular cells
Parafollicular Cells
- from neural crest cells
- in clusters between follicles
- larger than follicular cells
and stain less intensely
- secrete calcitonin triggered
by elevated blood Ca
- inhibits osteoclasts resorption
and stimulate osteoblasts
Structure
- 2 lobes connected by isthmus
- below larynx, rest on sides of trachea
- dense irregular CT capsule with septa dividing it into lobules
- each lobule has follicles surrounded by CT containing parafollicular cells (C or clear cells)
Function
- synthesize Thyroxine (T4) and Triiodothyronine (T3)
- they help control metabolic rates
- secretes calcitonin
- large amount of hormones stored in the inactive form in follicle (enough hormones to supply body for 3 months with no additional synthesis
General
- Ductless glands
- secrete hormones into vascular system
Composed of
- secretory cells of epithelial origin
- intervening connective tissue
- vascular and lymphatic capillaries
Exist as
- discrete organs (pit, thyroid, para, adrenal)
- associated with exocrine (pancreas)
- within other organs (kidney, testis, ovary, GI tract, brain)
-
Pancreas
Anatomy
- head connect to the duodenum
- body and tail to left side of body
-
Clinical Correlation
Type 1 IDDM
- childhood/adolescence
- loss of beta cells, autoimmune
Type 2
- adults, insulin resistance
- genetic factors and lifestyle
Parathyroid
Location and Structure
- 2 pairs, superior and inferior
- located on posterior surface of thyroid
- CT capsule continuous with the thryoid's
- septa divides them into lobules
- parenchyme = chief cells, oxyphil cells, and capillaries
Composition
Chief cells (principal)
- most numerous until childhood
- small with round central nuclei
and pale or eosinophilic cytoplasm
- secrete PTH which raises blood Ca
by increasing OC activity, stimulating
kidneys to reabsorb Ca, and promoting
Ca absorption in the small intestine via Vit D
Oxyphil Cells
- non-functioning, increase with age
- eosinophilic cytoplasm
- fluffy looking
Clinical Correlation
Hyperparathyroidism
Primary
most common cause if parathyroid
adenoma --> excess PTH --> excess
erosion of bone by OC and release of Ca
Secondary
kidney failure, lose lot of Ca in blood, increase
stimulation of parathyroids --> hyperplasia --> XS PTH
Hypoparathyroidism
- rare, only when ALL FOUR accidentally
removed during thyroidectomy
Adrenal Glands
Structure
Cortex MESODERM
-
General
- all zones stimulated by ACTH
- produces corticosteroids from cholesterol
- steroid-secreting cells: acidophilic
cytoplasm rich in lipid droplets
and central nuclei
- molecules diffuse freely, not from granules
bc they are lipid based
-
General
- sit on top of kidneys
- CT capsule with thin
septa, no hilum
Clinical Correlation
-
Hyperadrenalism
adenoma, carcinoma
or hyperplasia
Cushing's
glucocorticoids, moon face
-
Pheochromocytoma
- neuroendocrine tumor of medulla
originates in chromatin cells
- sympathetic NS hyperactivity
- High BP, palpitations, high HR,
weight loss, elevated glucose
Fight or Flight
- chromaffin innervated by preganglionic sympathetic neurons
- trigger release of epi and NE during
stress and intense emotional reactions
- both stimulate glycogen breakdown, elevating glucose
EPINEPHRINE
increases HR, dilates bronchioles,
dilates arteries of cardiac and skeletal muscles
NOREPINEPHRINE
contracts vessels of GI tract and skin,
blood flow to the heart, muscles, and brain