Microanatomy of Endocrine Flashcards
Development of Endocrine Glands
- developed from down growths of epithelium
- buds of cells are isolated from surface epithelium and supplied vascularly
Does an endocrine gland have any connection with the epithelial surface
no
What’s another name of the pituitary gland
hypophysis
Describe the location and shape of the pituitary gland
- small ovoid hanging from infundibular stalk from hypothalamus
- located in Sella Turcica ( depression ) of sphenoid bone
- enclosed by CT capsule
When does the pituitary gland development begin
3-4 weeks
Where is the anterior pituitary developed from
- budding of buccal ectoderm called the Rathke’s pouch
- cuts off from the buccal ectoderm and develops into anterior pituitary
- after it is cut off then sphenoid bone grows around it
Where is the posterior pituitary developed from
- down growth from brain tissue called neuroectoderm that comes into contact with upward movement of rathke’s pouch
- maintains it’s connection with Brain tissue unlike anterior pituitary
Where is the hypothalamus located
- floor of the third ventricle in the brain
- next to optic chiasm
What are the two parts making up the posterior pituitary and describe
1- infundibular stalk ( connects to hypothalamus )
2- pars nervosa
What are the three parts making up the anterior pituitary and describe them
1- Pars tuberalis ( thick wall around infundibulum )
2- Pars intermedia ( division between anterior and posterior )
3- Pars distalis ( makes up most of AP )
What is the hypophyseal fossa
the sella turcica in sphenoid bone
Why is the neurohypophysis lighter staining than adenohypophysis
- because it just has neurons and no glandular secreting cells
- doesn’t synthesis its own hormones just stains them
What is found histologically in the pars intermedia
- contains colloid filled like cysts
- remnants of rathke’s pouch
What are the two division of cells in the anterior pituitary
- chromophils : brightly stained
- chromophobes : pale staining
Describe Chromophils
- glandular cells arranged in cords or nests
- surrounded by capillaries
- two subtypes : Acidophils ( lighter ) and Basophils (more granules)
Describe Chromophobes
- exhausted chromophils
List the 5 types of cells in the anterior pituitary
1- Somatotrophs : growth hormone 2- Mammotrophs : prolactin 3- Corticotrophin : ACTH 4- Thyrotrophs : TSH 5- Gonadotrophs : FSH & LH
List the 5 cells types in the anterior pituitary in order of most to least numerous
1- somatotrophs ( 50 % )
2- Mammotrophs ( 20 %) , Corticotrophs ( 20% )
3- Thyrtotrophs ( 5%) , Gonadotrophs ( 5% )
What is the histological appearance of Posterior pituitary
- pale staining
- fibrous in appearance
- composed of unmyelinated axons of the cell bodies in the supraoptic and paraventricular nuclei located in hypothalamus
- herring bodies , pituicytes
- highly vascular
What are Herring Bodies
- dilations of axons for storage of hormones in posterior pituitary
What are Pituicytes
- support cells in posterior pituitary
Hypothalamic- Pituitary Neuroendocrine Link ( for posterior )
- Supraoptic nucleus and Paraventricular nucleus make oxytocin and ADH
- hormones travel down axons to posterior pituitary for storage
- releasing and inhibiting factors travel down axons to promote or inhibit the pleasing of hormones from nerve endings into surrounding capillary plexus which drains into hypophyseal vein
Hypothalamic- Pituitary Neuroendocrine Link ( for anterior)
- Hypothalamus releases hormones that are carried in blood to anterior pituitary through the hypophyseal portal system
What supplies the Posterior pituitary with blood
- inferior hypophyseal artery
- capillary plexus surrounds it
Describe the portal system in the anterior pituitary
- Hypophyseal portal system
- primary capillary plexus arises from superior hypophyseal artery and carries releasing hormones from hypothalamus to anterior pituitary
- secondary capillary plexus takes the hormones secreted by anterior pituitary and drains into hypophyseal vein
What does the hypophyseal vein rain
anterior and posterior pituitary
What is the location and shape of the thyroid
- anterior and lateral surface of the upper trachea
- bilobed
- level C5 and T1
What is the thyroid gland composed of anatomically
- two lobes connected by a band
- has 4 parathyroid glands that sit superior and inferior of each thyroid lobe
- highly vascular
What is the purpose of the parathyroids
- regulation of calcium levels
- especially in smooth muscle contraction
Can you live without the parathyroids
- no
- muscles won’t be able to contract
What is the thyroid gland composed of histologically
- vascular structure made of spherical storage units
- made of follicular cells lined with simple cuboidal epithelium ( thyrocytes )
- parafollicular cells ( c ) on outside of follicle
Histologically describe Follicular cells and function
- lined with microvilli
- filled with colloid that stores thyroglobulin ( inactive storage form of T3 & T4 )
- produce T3 & T4
Histologically describe paraollicular cells and their function
- larger paler staining cells around follicular cells
- produce calcitonin to regulate body calcium levels
- calcitonin act on osteoblasts to increase bone formation and decrease calcium blood levels
Histological effects of hyperthyroidism and hypothyroidism on colloid
- hyperthyroidism = decreased colloid
- hypothyroidism = increased colloid
What is the histological presentation of the adrenal Glands
- highly vascular glands surrounded by CT capsule
- embedded in perirenal fat at superior poles of kidneys
What is the histological presentation of the adrenal cortex zones
- Zona glomerulosa : rounded groups of cells
- Zona fasciculata : large vacuolated cells in columns
- Zona reticularis : cells arranges in branching irregular networks
What cells is the adrenal medulla are made of
neural crest cells
What is the GEP
gastrointestinal enteroendocrine pancreatic system
- hormone secreting glands in GI and pancreas
What are enteroendocrine cells
- sporadic endocrine hormone producing cells that are spread as clusters in the gastrointestinal pancreatic system
- arranged in gastrointestinal epithelium
- secrete hormones controlling gut function
