ENDOCRINE SYSTEM is what?
ENDO = internal CRINE- secrete
* Main role: secrete hormones
* Distribution: glandular, cluster, individual cells.
ENDOCRINE GLANDS
* Islands of secretory epithelial cells.
* ductless so, hormones are discharged into the interstitial spaces and into the bloodstream.
* have target organs.
* Morphology: Clump, cord, clump and cord, follicular
- HORMONES
- Steroids (E.g. cortisol, testosterone)
- Amino acid derivatives (E.g. Thyroxine, epinephrine)
- Peptides and proteins (E.g. Insulin, growth hormones)
- Reproduction
- Growth and development
- Mobilization of body defences
- Maintenance of much of homeostasis
- Regulation of metabolisms
how do the messenger systems between endocrine and nervous differ
Endocrine:
Control: Endocrine reflexes
Effectors: All tissues
Target cells: Throughout the body
Secretion: Hormones
Specialized cells: Glandular epithelial cells
Speed and duration of effect: Slow Long lasting
NERVOUS
Control : nervous reflexes
Effectors: Muscles and glands
Target cells: Post-synaptic cells in the
muscles and glands.
Secretion: Neurotransmitters
Specialized cells: Neurons
Speed and duration of effect: Fast Short-lived
HYPOTHALAMUS
- The “brains of the brain” found in brain
- Made up of nuclei (clusters of neurons).
- Attached to the posterior pituitary gland via
infundibulum. - Linked to anterior pituitary gland via hypophyseal portal system
- Neuroendocrine function.
- Control autonomic regulatory activities and endocrine homeostatic systems
- manages all endocrine hormonal levels, sensory processing and organizing body metabolism, appetite and thirst.
PARTS OF THE ENDOCRINE SYSTEM
- MAJOR ENDOCRINE GLANDS
- ENDOCRINE COMPONENTS WITHIN OTHER SOLID ORGANS
- DIFFUSE ENDOCRINE SYSTEM (DNES)
- MAJOR ENDOCRINE GLANDS:
* Synthesis, storage and secretion of hormones. - ENDOCRINE COMPONENTS WITHIN OTHER SOLID ORGANS:
* Clusters of endocrine cells with other solid organs * E.g. kidney, heart, liver. - DIFFUSE ENDOCRINE SYSTEM (DNES)
* Scattered individual hormone cells with paracrine secretion effect - affecting neighbouring cells. E.g. neuroendocrine
cells in the gastrointestinal and respiratory tracts.
* Endocrine secretion effect - producing systemic effects.
PITUITARY GLAND
- AKA: hypophysis.
- “Master endocrine gland”
- Size and shape of a pea.
- Comprised of two separate glands from different embryological processes:
Posterior pituitary gland.-neurophypophysis - Downward projection of the brain – nervous tissue.
- Retains a direct connection with the base of the brain.
- Connects to the hypothalamus via infundibulum
*hypothalamus to hormone via neurosecretory cell
Anterior pituitary gland. – adenophypophysis
* Upward projection of Rathke’s pouch – glandular epithelial tissue.
* “Attaches” itself to the posterior pituitary gland.
* Indirectly connected to the hypothalamus by the hypophyseal portal tract.
Hormones released into the posterior
pituitary gland
Hormones released into the anterior
pituitary gland
Hormones released into the posterior pituitary gland-(move down axons):
ADH (antidiuretic hormone):
* informs kidney of h2o conservation.
* regulates and balances the amount of water in your blood.
Oxytocin:
* social bonding, sexual reproduction, childbirth and milk secretion after delivery.
The hypothalamus secretes hormones and sends them down the axon via neurosecretory cells to posterior pituitary and act directly on NON ENDOCRINE tissues
Hormones released into the anterior
pituitary gland -(pass through the hypophyseal portal system)
Releasing hormones:
* Regulates the release or synthesis of anterior pituitary hormones.
Inhibiting hormones:
* Inhibits the production of anterior pituitary hormones.
releasing and inhibiting hormones are produced by neurons and portal vessels to target the anterior pituitary gland
ANTERIOR PITUITARY histology and its cells
Three subdivisions:
Pars distalis - Cellular. Clump and cord.
Pars intermedia-separates anterior from posterior
* Cysts with eosinophilic material.
* Remnants of Rathke’s pouch.
- basophilic cells present
Pars tuberalis- on the tuberalis wraps around the infundibulum -clump and cord
Cells are:
Chromophils – cells that can pick up stain.
* Acidophils -hormone-containing granules in cytoplasm that stain with acidic stain. - RED
* Basophils -hormone-containing granules that stain with basic stain. only on staining ability
Chromophobes – cells with sparse or no granules.
* They do not stain with either acid or basic stains
POSTERIOR PITUITARY histology and its structures
NEUROYPOPHYSIS
Pars nervosa
* Contains axons and axon terminal ends of the neurons.
* HERRING BODIES are the expanded axons that contain granules with hormones (oxytocin and ADH). * terminal end of the axons from hypothalamus. * Temporary storage of hormones before release.
infundibulum
* Extension of the hypothalamus.
* Consist of axons from neurons.
PP contains
* Non-myelinated axons EXTENDing from the hypothalamus
* Secretions passed down the axons supported by pituicytes -non-secretory, glial cells (support cells)
hypophyseal portal vessel connects anterior to posterior
ANATOMY OF THE THYROID
- Butterfly shaped gland with two lateral lobes connected by tissue called isthmus
- below the larynx; anteriorlateral surface of the trachea.
Functional units
* Thyroid follicles – secrete thyroglobulin – T3 and T4 hormones. which help to Increases metabolism.
Morph of the follciles
* Glandular morphology: Follicular/glandular
* Surface morphology: Simple cuboidal with microvilli.
* Capsule – DICT.
* Sepate into lobules.
- Follicles of variable sizes- Active/Inactive filled with colloid containing thyroglobulin
Active cells are taller with more cytoplasm they have pale Large nuclei. Extraction of colloid from the lumen of the follicle seen by the large white parts in the lumen- actively absorbing thyroid hormone.
Inactive : Colloid homogenously distributed and Filled with thyroglobulin.pink lumenal area in the middle instead of clear. There is microvilli to increase surface area to take in more hormone, No signs of colloid extraction - little to no white parts in the lumen . Cells are shorter or flat and have less cytoplasm-
PARAFOLLICULAR CELLS - C cells.
* Individual or clusters located in the interstitium (in between follicles).
*
Secrete calcitonin:
* Lowers blood calcium levels – suppress osteoclastic resorption of bone.
* Antagonistic to (PTH).
FEEDBACK CONTROL with thyroid
when your thyroid levels are low. Your hypothalamus releases thyroid releasing hormone (TRH), which triggers your anterior pituitary gland to release thyroid-stimulating hormone (TSH), stimulating the release of T3 and T4 from the thyroid.
whereas the rise of thyroid hormones in blood inhibits the secretion of TRH and TSH
ANATOMY OF PARATHYROID histology and cell types
- 4-5 tiny glands in the posterior surface of the
thyroid’s lateral lobes.Morphology: clump and cord - Irregular rows of cells.
- Secrete parathyroid hormone (PTH) antagonistic effect to calcitonin
- Regulates serum calcium and phosphate
levels.
- Raises serum calcium levels.
Capsule – DICT.
* Sepate divides parenchyma into lobules.
* Invasion of lymphocytes and adipose tissue with age.
CHIEF OR PRINCIPAL CELLS - dominant type
* Secrete PTH.
* Active – dark staining cytoplasm.
* Resting – pale staining cytoplasm.
* More numerous, smaller cells.
OXYPHILS
* Do not secrete PTH.
* Non-secretory cell type.
* Lesser in number, larger cell, eosinophilic cytoplasm.
*increase as you age
ADRENAL GLAND
- Two glands; each located on top of the kidneys. only endocrine gland with c/m
- Cortex- outer glandular region has three sublayers
ZONA GLOMERULOSA-
* Capsule: DICT
* secretory cells - clusters and clump.
* Separated by trabeculae.
* Cells have round nuclei and less cytoplasm.
* Secrete mineralocorticoid hormones: aldosterone- Controls sodium and water resorption.
ZONA FASCICULATA- Middle and broadest layer.
* columns and parallel cords of secretory cells.
* Separated by capillaries.
* Cells have large, pale cytoplasm due to lipid
content.
* Secrete glucocorticoids: cortisol- increases. glucose in the blood
*
ZONA RETICULARIS Thin, innermost layer.
* Branching cords and clusters of cells (separated by capillaries).
* Cells are smaller and darker staining – fewer lipid droplets.
* Brown lipofuscin pigments.
* Secrete androgens: testosterone
- Medulla -Epinephrine and norepinephrine
Neurosecretory tissue – neurons secrete their products into the blood.
Secretory cells: chromaffin cells -Contain catecholamine (hormones secreted in the adrenal medulla).
* Cells secreting epinephrine: Small, spherical neuroendocrine granules.
* Cells secreting norepinephrine: Larger neuroendocrine granules.
* Morphology: clump and cord.
* Hormones travel from the cortex into the medulla and drain into the central vein.
PANCREATIC ISLETS
- Islets of Langerhans.
- Exocrine - digestive enzymes into the small intestine and Endocrine - hormones into blood stream functions.
- Pancreatic islets produce hormones.
- Vary in size and most numerous in the tail.
- Morphology: clump and cord.
- Four types of cells joined by gap junctions.
Alpha cells - Glucagon -Stimulates the release of
glucose, which increases blood levels.
Beta cells - Insulin Stimulates glucose uptake
by muscle and liver cells and lowers blood glucose
Delta Somatostatin-Helps control digestion
and nutrient absorption
Pancreatic polypeptide (F or PP) cells-Regulates pancreatic secretion activities.
cells can be clustered or individual
PINEAL GLAND
- Small, pine nut shaped gland.
- Found in the midline of the brain
- Secretion: melatonin
- Affects the daily sleep/wake cycle and the
onset of puberty. - Levels are inversely proportional to the amount of sunlight – biological clock or circadian rhythm.
- Pinealcytes (pineal chief cells)
- Highly modified neurons surrounded by fenestrated capillaries.
- Morphology: clump and cord
- Neuroglial cells
- Similar to astrocytes of the CNS.
- Pineal sand - “Brain sand” - lots when you are aging - basophilic
- Calcified concretions (concentric layers of CaPO4 and MgPO4 ).
- Basophilic staining
- Age-related histological feature.
*location in skull can be used as a pathological guide
