Week 5 endocrine system Flashcards
What is the endocrine system?
- synthesis of chemical messengers- hormones
- disseminated via bloodstream to specific target organs or act locally
- coordinate and integrate bodily funcitons
What are endocrine organs generally composed of?
Islands of secretory epithelial cells with supporting tissue rich in blood and lymphatic capillaires
Where is the pituitary gland located?
Extension below hypothalamus
Name some of the target organs of pituitary glands
Breast, uterus - oxytocin
Kidneys - ADH
Ovaries/testes - FSH, LH
What is the origin of the Posterior (neurohyoiohysis)
- enuroectoderm
- downgroeth of nervous tissue form hypothalamus
- maintains link with hypothalamus by pituitary stalk (infanfibulum)
- stains a lot lighter - myelinated axons
What is the origin of the Anterior
(Adenohypophysis)
- oral ecoderm
- upgrowth form roof of primitive oropharynx
- rathke pouch
Loses attachment with oral cavity
Cleft separates by posterior and anterior
Pestigal
- left over form pouch
- forms part of pars intermedia
What controls the pituitary gland?
Hypothalamus
Hormones secreted by pituitary fall into 2 groups?
- Those acting on non-endocrine tissues
- Those modifying secretpry activity of other endocrine tissues
Give examples of type 1
Growth hormone
ADH
prolactin
Oxytocin
MSH
Give an example of type 2
TSH
ACTH
FSH
LH
What are the thyroid, adrenal, gonads known as?
Pituitary-dependent endocrine glands
Released continuously or in burst?
Usually bursts or circadium rhythms
Vary during menstrual cycle
What is the posterior pituitary site of storage and relase of?
2 hormones
- adh (vasopressin) - synthesised in supraoptic nucleus
- oxytocin - synthesised in paraventriclar nucleus
Both pass down axons of hypothalamo-hypophyseal tract, within the pituitary stalk
- stored in distended axon terminal
- nerve impulses form hypothalamus control release
What are herring bodies?
- posterior pituitary composed of non-myelinated axons
- cel bodies lie in supraoptic and paraventircular nuclei of hypothalamus
- secretory granules present all along axons
- most numerous in terminal distension where they meet capillarie s
What are the three divisions of the anterior pituitary?
- pars distalis
- pars intermedia
- pars tubularis
What is the fucntion of the anterior pituitary?
- hormone producitona nd secretion
- secretion regulated by hypothalamic releasing hormone
What is thr pituitary derived from?
Ectoderm
What are the main two cell tyoes of the anterior pituitary?
- darkly staining chromophils (basophils and acidophils)
- pale staining chromophobes
What are the two types of chromophil cells?
Acidophil and basophil
Mammotrophs
Increase during pregnanc
Somatotrophs
Abt 50%
Growth hormone
Descirbe the histology of the pars intermedia
- derived from remnants of rathke pouch
- composed of basophilic cells
- located between AP and PP
- systic structures containing colloid
- porduce poropiomelanocortin and MSh in foetal life
What is the thyroid gland controled by?
Hypothalamus
What hormones are released by thyroid?
TRH - stimulates thyroid cells to release TSH
- negative feedback loop
What is the histology of the thyroid gland
- basic unit is the follicles
- speroidla sturcutre lined by cuboidal epithelium
- vary in size filled with colloid
- gland divided into lonules by septae
What are the two major hormones produced by thyroid?
- Tri-iodothyronine (T3)
- Thyroxine (T4)
What do the hormones produced by the thyroid do?
- Regulate how wuickly the body burns energy, makes proeitns, contorls how sensitive the body is to other homones
- also porduces calcitonin
Thyroid gland inacitve
Thyroid gland acitve
Epithelial cells less suppressed
Thyroid C cells
Calcitonin produced by parafollicluar Ccells
- small clumps between follicles
- calcitonin physiological antagonist of parathyoid hormone
- lowers blood calcium levels
parathyroid gland
Small 2-5 mm glands, closely related to thyroid (posterior surface) two pairs in most ppl
histology of parathyroid gland
- parathyroid gland
- thyroid gland
- fibrous septum
What are functions of the parathyroid?
Bone, kidney, intestine - calcium into blood stream
descirbe the cell types of parathyroid cells
Two cell types
- principle or chief cells
- oxyphil cells
describe principal or chief cells
- small dark nuclei, pale cytoplasm
- most numerous
- secrete PTH
Describe ozyphil cells
- abundant pink cytoplasm
- not knwon to have secretory role
Adrenal gland
Adrenal gland anatomy
On top of kidneys
what are the two components of the adrenal gland
- adrenal cortex and medulla
The adrenbal cortex seretes which hormones?
Steroid hormones
Give examples of steroid hormones produced by adrenal cortex
- mineralocorticoids
-> fluic and electrolyte balance - glucoocorticoids
-> carbs and lipid balance - sex hormones
name the three zones in the adrenal cortex
- zona glomerulosa
- zona fasciculata
- zona - reticularis
What does the zona glomerulosa do
- cell clusters separate by fibrous septae
- secrete mineralcorticoids
- mainly aldosterone - acts on renal tubules to increase sodium and water retention
What does the zona fasciculata do?
- columns of cells with abundant pale cytoplasm
- one cell thick separated by capillaries
- secrete glucoocorticoids, mainly cortisol
What does the zona reticularis do?
- irregular groups of cells
- separated by wide calibre capiries
- source of adrenal androgens, DHEA, DHEAS and glucocorticoids
Descirbe the histology of the adrenal medulla
- cluster of cells with granular, basophilic cytoplasm
- very vascular
- secrete adrenaline and noradrenaline
- tun brown in chomiun salt fixative = chormaffin cells
- cells secreting neuroadrenaline (Na) more strongly postive
Descirbe the cells contianed in the endocrine pancreas
- islets of langerhands
-> most numerous in tail
-> groups and strands of cells around capillary network - 3 tyoes of cells:
Alpha - glucagon
Beta - insulin
Delta somatostatin
what is the funciton of the pineal gland?
Synthesis of melatonin - induces rthyhmical changes in endocrine activity
Pinealocytes
Secrete melatonin into capillaries via long axons modified neurons
Neuroglial cells
Support pinealocytes are modified astrocytes
Basophilic pineal sand
Dalts of calcium magnesium and silicon - feature of aging gland
Descirbe the histology of pineal glands
- small dark nuclei belond to the astrocytes found in pineal gland
- pinealocytes have alrger, lighter and round nculei surrounded by brad rin of light cytmoplasmm , most nuclei present are nuckei pinealocytes
- endothelial cell nuclei found in association wihth vesels and capillaries traverisn the tissue
What do pinealocytes and astrocytes have in common?
Lonf processes which give the tissue between the nuclei its stringy appearance
Describe the diffuse neuroendocrine system
- scattered neuroendocirne cells
- GI systme
- respiratory system
Descirbe the GI system
Secretions include gastin, secretin, somatostatin
VIP (vascoactive intestinal peptide)
Descirbe the respiratory system
- secretions include serotonin, calcitonin, bombesin
- act in endocrine or paracrine fashion
