Endocrine System 😌 Flashcards
Components of the Endocrine System:
- 4 Major Endocrine Organs
- 4 Endocrine components w/in solid organs
- 2 Diffuse neuroendocrine system (DNES)
Major Endocrine Organs:
Pituitary, Pineal, Adrenal, Thyroid - Gland
Endocrine components w/in solid organs:
Pancreas, Testis, Ovary, Kidneys
Diffuse neuroendocrine system:
Most of the time scattered in GIT, Respiratory tract
Pituitary gland
- Other name
- Housed where?
- Parts
- Hypophysis cerebrii
- Housed in sella turcica
- Adenohypophysis (anterior part) and Neurohypophysis (posterior part)
What is the master endocrine gland?
Pituitary gland
Embryology of the Pituitary gland
- Originates from which structure/s?
- How is it formed?
- Partly from the developing brain (neural ectoderm) and partly from the developing oral cavity (oral ectoderm)
- 3rd week of development:
Neurohypophyseal bud grows caudally from the diencephalon but it is still connected through the future infundibulum -> becomes the posterior pituitary
An outpocketing grows cranially from the roof of the pharynx and eventually becomes the anterior pituitary
Late 2nd month of development:
The hypophyseal pouch would detach from the roof of the pharynx and merge with the neurohypophyseal bud.
Fetal period:
During this period, the anterior and posterior parts of the pituitary would complete their development.
Determine the divisions of the Pituitary Gland
- Typically glandular
- Resemble CNS tissue
- Dark-staining
- Pale staining
- Adenohypophysis/Anterior lobe
- Neurohypophysis/Posterior lobe
- Adenohypophysis
- Neurohypophysis
Pars distalis
- Relative size and location
- Group of cells
- Largest and most anterior
- Chromophils - secretory cells of the anterior pituitary with hormones stored in the cytoplasmic granules; further classified into acidophils and basophils
Acidophils:
>Somatotophs (constitute half the cells in PD)
>Lactotrophs: PRL
Basophils:
>Corticotrophs: synthesize POMC which forms ACTH and LPH upon cleavage
>Gonadotrophs: FSH & LH
>Thyrotrophs: leas abundant
Chromophobes:
- few to no secretory granules
- have pale nuclei and cytoplasm
- SMALLER than chromophils
- represent a heterogeneous grp including SCs, undx progenitor cells
Funnel-shaped region hugging around the infundibulum of the neurohypophysis. What cells does this area contain?
Pars tuberalis
>Contain mostly gonadotrophs
Thin zone of basophilic cells between pars distalis and pars nervosa. Cells?
Pars intermedia
>Often invaded by basophils and chromophobes
>Usually contain small, colloid-filled cysts of various sized derived from the lumen of the embryonic hypophyseal pouch
Neurohypophysis (Posterior Pituitary)
- Composition
- Unique char in relation to hormones
- Consists mainly of unmyelinated axons of large secretory neurons with cell bodies in the supraoptic and paraventricular nuclei of the HP
- DOES NOT contain the cells that synthesize the two hormones it stores (ADH and OT)
Pars Nervosa
- Location
- Function
- Translocation of hormones down the hypothalamic-hypophyseal tract utilizes this protein
- Neurohypophysis (Posterior pituitary)
- Storage site of OT and ADH
- Neurophysin
Infundibular stalk
- Location
- Function
- Neurohypophysis
2. Bridges the hypothalamic and hypophyseal regions in the median eminence
Identify the type of cell in the posterior pituitary.
- Highly branched glial cells that resemble astrocytes (helper cells) because it comes from diencephalon
- Most abundant cell type in posterior pituitary
- Axonal dilatations where hormones accumulate
- Pituicytes
- Pituicytes
- Neurosecretory bodies (Herring Bodies)
Hormones of the posterior pituitary gland? Synthesized where? Function?
- ADH/Arginine Vasopressin
- synthesized in the supraoptic nucleus
- increases water permeability of renal collecting ducts - Oxytocin
- synthesized in the PVN
- stimulates contraction of the mammary gland myoepithelial cells and uterine smooth muscle
Hypothalamic-Hypophyseal Tract System
- Pathway
- ADH and OT undergo what transport and accumulate where temporarily before release and uptake by what?
- What enables distribution of the hormones throughout the body? Be specific.
- SON + PVN -> infundibulum -> Pars Nervosa of Neurohypophysis
- ADH and OT undergo axonal transport and accumulate temporarily in the axons of the hypothalamic-hypophyseal tract before release and uptake by capillaries
- Inferior hypophyseal artery
Hypothalamic-Hypophyseal Portal System 1. Carries neuropeptides from where to where? 2. Blood supply? 3. Venous drainage? 4. Superior Hypophyseal Arteries >Supplies what? >Divides into what as it passes down the infundibulum. Branches? 5. Inferior Hypophyseal Arteries >Supplies what? >Arises as a single branch from?
- From the median eminence to the adenohypophysis to simulate or inhibit hormone release by endocrine cells
- Internal Carotid A.
- Hypophyseal V.
- Superior Hypophyseal Arteries
>Supplies the median eminence and infundibular stalk
>Divides into anterior and posterior branches as it passes down the infundibulum
>Branches:
A. artery of trabecula - goes down to supply pars distalis
B. Primary plexus of fenestrated capillaries which rejoin to form venules that branch again as larger secondary capillary plexus in your adenohypophysis - Inferior Hypophyseal Arteries
>Supplies neurohypophysis
>From ICA
Identify.
1. Hyperactive corticotrophs which release ACTH which stimulates adrenal glands to increase secretion of corticosteroids
- Hypersecretion of somatotrophs
A. In childhood = proportionate growth
B. During adulthood = disproportionate growth - Hypersecretion of most pituitary hormones due to a benign tumor
- Cushing’s disease
2.
A. Gigantism
B. Acromegaly
- Pituitary Adenoma
Pineal gland
- Other term
- Function
- Histologically covered by?
- Embryonic origin
- Hormone
- Epiphysis cerebrii
- Regulates the daily rhythm of bodily activities
- CT of the pia mater
- Neuroectoderm in the posterior wall of 3rd ventricle
- Melatonin
- regulates/promotes sleep in humans
- production is influenced by the detection of light (inhibited) and dark (promoted) by the retina
Identify the structure in the pineal gland
- Major secretory organ, Basophilic cytoplasm, irregular euchromatic nuclei
- Modified astrocytes, elongated nuclei that are more heavily stained than #1, usually found in perivascular areas between groups of #1
- The “brain sand”, extracellular mineral deposit with no apparent significance, excellent marker for pineal gland
- Pinealocyte
- Glial cells
- Corpora arenacea
Thyroid gland
- Located anterior and inferior what structure
- Consists of two lobes united by?
- Embryonic origin
- Hormone/s
Thyroid gland
- Larynx
- Isthmus
- Foregut endoderm near base of developing tongue
- T3, T4, Calcitonin
Embyonic Development of the Thyroid Gland?
3rd week: Begins as an entodermal thickening in the midline of the pharynx floor between tuberculum impar and copula —> Thickening involutes to become the thyroglossal duct —> Duct elongates and its distal end becomes bilobed —> Bilobed terminal swellings becomes the thyroid gland —> Gland migrates inferiorly in the neck —> By 7th week, it reaches final position wrt trachea and pharynx
Thyroid gland neurovasculature Arterial Supply 1. Superior thyroid artery >Branch of >Accompanied by? >Mainly supplies what?
- Inferior thyroid artery
>Branch of?
>Supplies what?
Venous Drainage (3)
Lymphatic drainage (2)
Innervation (3)
- Superior thyroid a.
>Branch of ECA
>Accompanied by external laryngeal n.
>Mainly supplies the anterosuperior aspect of the gland - Inferior thyroid artery
>Branch of thyrocervical trunk
>Supplies posteroinferior aspect of the gland
Venous Drainage:
Superior, Middle, Inferior Thyroid V.
Lymphatic Drainage
>Mainly drains into deep cervical lymph nodes
>Few lymph vessels descend to the paratracheal nodes
Innervation
>Superior, Middle, Inferior Cervical Sympathetic Ganglia
Identify the structure in the thyroid gland.
1. Composed of millions of rounded, epithelial, colloid-filled thyroid follicles
- Filled with large gelatinous protein (thyroglobulin)
- Cells lining the thyroid follicle.
>Epithelium classification/s? - Found in the basal lamina of follicles or isolated in clusters; larger than #3; derived from neural crest cells; more uniform in size than #3.
- Parenchyma
- Colloid
- Thyrocytes/Follicular cells
>If active, low columnar. If hypoactive, squamous - C cells/Clear Cells/Parafollicular cells
Chronic dietary iodine deficiency?
Goiter
Parathyroid glands
- Embryonic Origin
- Location, specific embryonic origin
- Pharyngeal Pouches
2.
A. 2 superior parathyroid glands (PTH IV)
>More constant position
>Lies ~1cm superior to pt of entry of inferior thyroid arteries
>Dx from 4th pharyngeal pouch
B. 2 inferior parathyroid glands (PTH III)
>Position may vary among individuals
>Dx from 3rd pharyngeal pouches
Neurovasculature of the Parathyroid Glands
Blood supply
1 main
5 others
Venous Drainage (1)
Lymphatic Drainage (2)
Innervation (1)
Blood supply:
>Inferior thyroid artery
>Others: Superior thyroid arteries, thyroid ima a., laryngeal a., tracheal a., esophageal a.
Venous Drainage Parathyroid veins (draining into the thyroid plexus of veins of the thyroid gland and trachea)
Lymphatic
>Deep cervical LN
>Paratracheal LN
Innervation
>Vasomotor, NOT secretomotor!!
>Thyroid branch of the cervical (sympathetic) ganglia
Identify type of cells of the Parathyroid Gland
- Small polygonal, round nuclei, pale staining, slightly acidophilic cytoplasm, more abundant in younger people, secretes which hormone?
- Degenerated/transitional derivatives of principal cells exhibiting low levels of PTH synthesis
→ Larger than principal cells with very acidophilic cytoplasm
→ Smaller population and clustered
→ More common in older individuals; Replaces principal cells and thus accumulate with age
- Principal (chief) cells. Secrete PTH which raises blood Ca2+ lvls
- Oxyphilic (acidophilic) cells
Identify disease.
- Diminished secretion of PTH
▪ Bones become denser and more mineralized
▪ Striated muscles exhibit abnormal contractions due to an
inadequate concentration of calcium ions
2.
→ Increased secretion of PTH
>Stimulates osteoclasts for breakdown of bones
>Exhibited by increased blood calcium that can be deposited in cartilages, arteries, or kidneys
- Hypoparathyroidism
2. Hyperparathyroidism
Adrenal glands
- Other name
- Major attachment?
- Suprarenal glands
2. Diaphragmatic crura
Two concentric regions of the adrenal medulla
>Include their color and embryonic origin
- Adrenal Cortex
- Yellowish
- Mesoderm - Adrenal Medulla
- Reddish-brown
- Neural crest ectoderm
Dual blood supply of the adrenal medulla?
Medullary arterioles (arterial blood) and capillaries of the cortex (venous blood)
Adrenal cortex hormones
Cortisol and androgens
Three concentric zones of the adrenal cortex
GFR
Zona glomerulosa
Zona fasciculata
Zona reticularis
