endocrine (anat) Flashcards
endocrine system
- Communication and regulation in response to: body homeostasis
○ Normal physiologic changes in body
○ Alterations in external environ - Distinct glands or tissues
○ Secrete organic compounds
○ Chemical messengers (HORMONES) - Stimulate/ cause change in metabolic activity in target tissues/ organs
principal endocrine glands
pituitary gland
thyroid, parathyroid
pancreas, adrenals
endocrine gland
rich blood supply with fenestrated capillaries
secretory cells (cuboidal/ columnar epithelium)
cells arranged in cords/ clusters
supportive framework (connective tissue)
HORMONES
○ Biologically active sub released and transported in blood stream
○ Act on target organs/ paracrine/ autocrine
○ 4 major types: affects if binds intracellular or surface
§ PROTEIN, peptide: long/ short chain of aa
§ STEROIDS: lipid cholesterol
§ AMINO derived/ Tyrosine: aa with modified grps
§ FATTY ACID derivative: etc polyunsaturated FA (prostaglandins, leukotriene, thromboxane)
Pituitary gland – MASTER endocrine gland structure
Base of brain PITUITARY GLAND + hypothalamus = neuroendocrine unit
- anterior pituitary (PARS tuberalis, intermedia, distalis)
- posterior pituitary (neural stalk, pars nervosa)
Pars tuberalis (ant.)
○ Undifferentiated cells (Gonadotrophs = FSH, LH)
○ Many cells appear to be Chromophobe cells
- Some acidophils, basophils also present
Pars intermedia
○ Follicles
○ Cystic follicles
○ Melanotrophs = Melanocyte stimulated hormone
Pars distalis
○ Sinusoidal capillaries
- Chromophils: Secretory cells, hormones stored in cytoplasmic granules
- a-cells (acidophils)
○ Somatotrophs = growth hormone
○ Mammotrophs = prolactin - b-cells (basophils)
○ Gonadotrophs = FSH, LH
○ Corticotrophs = ACTH, corticotropin
○ Thyrotrophs = TSH
- a-cells (acidophils)
- Chromophobe cells
○ Degranulated chromophil cells
Hormones PRODUCED anterior pituitary
Follicle-stimulating hormone (FSH, LH) – gonadotrophs
○ Act on gonads (testes, ovaries)
Prolactin - mammotroph
○ Act on mammary glands, testes
growth hormone - somatotroph
○ Act on all body tissues, bone, muscle, adipose connective tissue
Adrenocorticotropin ACTH - corticotrophs
○ Act on adrenal cortex
Thyroid-stimulating hormone (TSH) - thyrotrophs
○ Acts on thyroid gland
MSH (melatonin) - melanotrophs
○ Acts on melanocytes in epidermis
Posterior pituitary structure
Neural stalk
Pars nervosa
- capillaries
- hypothalamic hormones stored in NEUROHYPOPHYSIS (granules in axons): ADH, oxytocin
pars nervosa
- Axons of neurosecretory cells in supraoptic nucleus (SON) & paraventricular nucleus (PVN) of hypothalamus
* Extension of hypothalamus - Cells:
* Pituicytes (supporting cells)
§ Ensheath axons
* Herring bodies (axons)
§ Granules of hormones stored - ADH, oxytocin - capillaries (large n.o. present)
hypothalamic hormones in pituitary gland
ADH – acts on renal tubules, reduce urine flow (incr water ab for BP)
Oxytocin – uterine contraction during labour, milk expulsion from mammary gland
Social interaction
Blood supply of pituitary gland
internal carotid artery branch
- Primary capillary plexus (superior hypophyseal arteries)
○ Stalk & median eminence - Hypophyseal portal veins
- 2nd cap plexus –> Ant pituitary
- Hypophyseal veins
- Inferior hypophyseal arteries –> Post pituitary
ANTERIOR pituitary secretion controlled by
1, 2 capillary plexus
- Control by hypothalamic hypophyseal portal system (1* & 2* cap plexus)
- Blood vessels
- Additional control: negative feedback
○ Plasma levels of hormones secreted by anterior pituitary
POSTERIOR pituitary secretion controlled by
- Control by hypothalamic hypophyseal tract (AXONS)
- neurons
- Pars nervosa
Hormone grp of pituitary glands
1) Directly acting on non-endocrine tissues
- GH, prolactin, ADH
2) Hormones modulating activity of other endocrine glands
- TSH, ACTH, FSH, LH
what is not under pituitary control
Pancreas, adrenal medulla, parathyroid not under pituitary control
disorders related to pituitary gland
- Adenomas of adenohypophysis
- Incr GH
- Gigantism in children
- Acromegaly in adults
- Cushing disease
- ACTH
- Stimulates adrenal glands –> more cortisol
- Diabetes insipidus
- Damage neurohypophysis (from head trauma)
- ADH/ vasopression insufficiency
- Incr urine production
Thyroid gland location
Located in ant and inferior to larynx in neck
Butterfly shape gland
- 2 lobes
- connected by isthmus
Capsule: richly supplied by superior and inferior thyroid arteries
Develops from foregut endoderm near base of developing tongue
thyroid gland cells
- Follicular cells
○ Cuboidal –> Tall columnar type
○ Active or non-active - Colloid contains THYROGLOBULIN (for T3, T4 bind to)
○ Under TSH control - Parafollicular cells
○ Develop from neural crest
○ Larger than follicular cells
○ LIGHTER STAINS
○Secrete calcitonin
hormones from thyroid gland
follicular cells = T3, T4 (regulate BMR, influence growth, nervous tissue maturation)
parafollicular cells = calcitonin (regulate blood Ca lvl, decr Ca)
disorders of thyroid gland
- Overproduction of thyroid hormones
- Underproduction of thyroid hormones
- Thyroid nodules
- Thyroiditis = inflam
- thyroid neoplasms (tumour)
- goitre (enlarged thyroid, TSH TSI)
parathyroid glands structure
4 ovoid masses lying posterior surface of thyroid gland (within capsule)
- secretes the PTH (raise blood Ca lvl)
parathyroid gland cells
- Chief cells
- Small polygonal cells with round nuclei
- Pale staining cytoplasm
- Oxyphil cells
- Large cells
- Acidophilic
Older people (degenerated chief cells)
