Endocrine System Flashcards
o Synthesized in the neuron cell bodies of the paraventricular nucleus of the hypothalamus.
o Main action:
✓ Induce strong contractions of smooth muscles in uterus resulting in childbirth.
✓ Oxytocin stimulates the contraction of myoepithelial cells around the alveoli and ducts in the lactating mammary glands, ejecting milk into the excretory ducts and the nipple.
Oxytocin
✓ make up the majority of cells population
✓ polyhedral cells
✓ less intensely staining (faintly acidophilic)
✓ 7 – 10 microns in diameter
✓ Vesicular nucleus
✓ Each cell has single cilium that extends into narrow canaliculi
✓ Cytoplasm contains secretory granules (Lipofuscin pigment
and Glycogen)
✓ Secretes PARATHORMONE (PARATHYROID HORMONE)
Principal cells/ chief cells
✓ decreases serum calcium levels
✓ unbranched single polypeptide chain
✓ made up of 32 amino acids
✓ MW: 3,400
Thyrocalcitonin
- Also known as the neurohypophysis or the pars nervosa
- Derived from the down growth of nervous tissue from the hypothalamus joined by the pituitary stalk
- Largely composed of non-myelinated axons of specialized neurons. The cell bodies of these neurons are located in the supraoptic and paraventricular nuclei of the hypothalamus.
- Axons are supported by specialized highly branching glial cells called pituicytes:
with oval nuclei and cytoplasm containing small amounts of yellowish-brown
pigment.
Posterior pituitary
Mediates sodium reabsorption
Aldosterone
e.g. adrenal cortical hormones, ovarian and testicular
hormones
Steroids derived from cholesterol
✓ Singly, solitary or in small groups
✓ Interspersed among the principal cells
✓ Deeply acidophilic, more intensely staining
✓ Dark central nuclei (smaller and more compact)
✓ Less in number
✓ Unknown Function (no hormonal secretion or secretion is unknown)
Oxyphil cells
The 3 subdivisions of the anterior pituitary
- Pars distalis/pars anterior
- Pars tuberalis
- Pars intermedia
Small, flattened endocrine glands which are closely applied to the upper pole of each kidney.
Adrenal (Suprarenal) Gland
Subdivision of the anterior pituitary that surrounds the neural stalk
Pars tuberalis
The 2 hormones released by the posterior pituitary
- Antidiuretic Hormone (ADH)/Vasopressin
- Oxytocin
- Small ovoid/spherical, yellowish-brown, highly vascular, ductless endocrine glands
- Location: Posterior surface of thyroid gland
- Normally, 4 of it are usually located at the middle 3rd of the thyroid (some can be at the lower 3rd)
- Size: 3-8mm in length, 2-5mm in width, .5-2mm in thickness
- Weight: 0.5-3 grams
- Supporting framework: reticular connective tissue
Parathyroid gland
- Small with round central nuclei and pale eosinophilic or clear cytoplasm.
- Secrete parathyroid hormone (PTH) / parathormone
- Active cells stain more intensely because of an increase in the number of rough ER.
- Resting cells, on the other hand, have pale cytoplasm and make up 80% of the
total in normal adults.
Chief or principal cells
Small oval glands closely associated with the thyroid gland. There are usually 2 pairs in mammals.
Parathyroid gland
- Regulates (lowers) blood calcium levels in conjunction with the parathyroid
hormone - Secreted by C cells or parafollicular cells found in the thyroid gland as
individual scattered cells in the follicle lining, or as small clumps in between
follicles.
Calcitonin
- Constitute about 20% of the anterior pituitary mass
- Secretes adrenocorticotrophic hormone
(ACTH)/corticotrophin
Corticotrophs
- Lies in the center/ inner part of the adrenal gland
- Cells are also arranged in small cords. The cells are modified postganglionic
sympathetic neurons that have lost their axons and dendrites during
development. - Synthesize and secrete catecholamines (primarily epinephrine and
norepinephrine).
Adrenal medulla
Outer part of the adrenal gland
Adrenal cortex
Less numerous and appear as cells that contain blue staining granules.
Basophils
- overproduction of aldosterone by one or both adrenal glands.
- The most common sign is high blood pressure that is difficult to control,
even with medication. - Some people also have symptoms such as: headaches muscle weakness or cramps heart
palpations - Unless it is treated and controlled, high blood pressure increases your risk of having a stroke,
heart disease or kidney disease.
CONNS’ DISEASE/ PRIMARY ALDOSTERONISM
e.g. insulin, growth hormone, parathormone
Protein and Glycoprotein molecules
- Iodine containing hormones
- Regulate basal metabolic rate and influences growth and maturation of nerve
tissue - Secretion of these hormones is regulated by TSH
T3 and T4
Butterfly-shaped endocrine gland lying in the upper neck of the trachea
Thyroid gland
Cells become taller, have more numerous microvilli, more organelles (more mitochondria, larger Golgi bodies, more numerous lysosomes, more developed endoplasmic reticulum),
increase in size and number
THYROTOXICOSIS/ TOXIC GOITER/ EXOPHTHALMIC GOITER
✓ Thin innermost layer and lies next to the renal medulla
✓ Consists of an irregular network of branching cords and clusters of glandular
cells separated by numerous capillaries
✓ The cells are much smaller than those in the zona fasciculata
✓ The cytoplasm is darker staining because it contains fewer lipid droplets
✓ Secretes small quantities of androgens and glucocorticoids
Zona reticularis
- Aka Water clear cells
- between the oxyphil and principal cells
Intermediate oxyphil cells
- Dense homogenous gelatinous material that represents extracellular storage form of the secretion of follicular cells
- Contains the following:
✓ Stored thyroid hormones: Thyroglobulin (a glycoprotein)
✓ Mucoproteins
✓ Proteolytic enzymes (separate hormone from its carrier)
✓ Desquamated cells
✓ Macrophages (rare)
Colloid
The 3 histological zones of the adrenal cortex
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
diffuse toxic goiter
PLUMMER’S SYNDROME
Cells with strongly staining cytoplasm
Chromophils
e.g. thyroxine, epinephrine (adrenaline), and norepinephrine
(noradrenaline)
Amino acid derivatives
- release discharge directly into the blood stream or lymph stream
- ductless glands
ex: Pituitary gland, Pineal Gland, Thyroid, Parathyroid, Adrenal, Testis, Ovaries
Endocrine
- Bi-lobed ductless reddish-brown highly vascular
endocrine gland - Location: at the anterior neck, extending from mid-
thyroid cartilage up to 6th tracheal ring - Size: 5cm in length, 4 cm in width, by 2 cm in thickness
- Weight: 25-40 grams
- Function: well-defined mechanism for extracellular
storage of thyroid hormones; synthesis, storage and elaboration of thyroid hormones T3 and T4
Thyroid gland
- Occur in nodules
- Copious eosinophilic cytoplasm packed with mitochondria
- Do not secrete PTH and increase in number with age.
Oxyphil cells
- Compromise up to 20% of the anterior pituitary, increasing in number during pregnancy.
- Secretes prolactin, which controls milk production
Mammotrophs (lactotrophs)
- autoimmune disorder in which the person produces antibodies
- mimic the action of thyroid-stimulating hormone (TSH).
- A primary sign is an enlarged thyroid, which may be two to three times its normal size.
- Patients suffering from this often have a peculiar edema behind the eyes, called exophthalmos, which causes the eyes to protrude.
- Treatment may include surgical removal of part or all of the thyroid gland (thyroidectomy), the use of
radioactive iodine to selectively destroy thyroid tissue, and the use of antithyroid drugs to block
synthesis of thyroid hormones
GRAVES’ DISEASE
Functions to raise blood calcium levels
Parathyroid hormone (PTH) / parathormone
flat or cuboidal
Inactive
- Synthesized in the neuron cell bodies of the supraoptic nucleus of the
hypothalamus. - Main action: increase water permeability in the distal convoluted tubules and
collecting ducts of the kidney. As a result, more water is reabsorbed and
retained in the body, creating a more concentrated urine.
Antidiuretic Hormone (ADH)/Vasopressin
- Increases serum calcium levels
- Single unbranched polypeptide chain has no cysteine
- MW: 9,000
Parathormone (Parathyroid hormone)
It increases blood glucose levels and increase cellular synthesis of glycogen.
Cortisol
tall and columnar
Active
The largest part of the anterior pituitary
Pars distalis/pars anterior
- General dryness (no secretions)
- Clinical triad:
▪ Dry eyes (keratoconjunctivitis)
▪ Dry mouth (xerostomia)
▪ Rheumatoid arthritis
SJOGREN’S SYNDROME
- more abundant (90%)
- less potent
- longer acting (6 to 7 days)
Tetraiodothyroxine /Thyroxine (T4)
The thin cell layer between the pars distalis and the
neurohypophysis. Synthesizes and secretes melanocyte-stimulating hormone
(MSH).
Pars intermedia
System responsible for the synthesis and secretion of chemical messengers known as hormones.
Endocrine system
- Make up 5% of the anterior pituitary
- Secretes follicle stimulating hormone (FSH) and luteinizing
hormone (LH)
Gonadotrophs
e.g. vasopressin, products of enteroendocrine cells
Small peptide molecules
- Make up 5% of the anterior pituitary
- Secretes thyroid stimulating hormone (TSH)/thyrotrophin
Thyrotrophs
- Also called the adenohypophysis
- Arises as an epithelial up growth from the roof of the primitive oral cavity known as the Rathke’s pouch.
Anterior pituitary
- Aka Mitochondria-rich cells/ C-cells
- Origin: Ectoderm/ Neuroectoderm
- Located in the interfollicular spaces and also in the follicular epithelium
- Pale staining with intensely staining small nuclei
- Slightly larger than principal cells
- Cytoplasm have brown to black cytoplasmic granules
- Rich in alpha-glycerophosphate dehydrogenase
- Secrete THYROCALCITONIN
Parafollicular cells
➢ Small bean-shaped gland about 1cm across
➢ Located at the base of the brain beneath the third ventricle, sitting in a bony cavity in the
base of the skull (sella turcica)
➢ Connected to the hypothalamus via the pituitary stalk/infundibulum.
Pituitary Gland (Hypophysis)
- Most numerous, making up almost half of the bulk of the anterior pituitary
- Secretes growth hormones
Somatotrophs
Vitamin D absence among children
Rickets
More numerous and can be distinguished by their red staining granules
and blue nuclei
Acidophils
Cells with weakly staining cytoplasm. The cytoplasm appears clear
indicating the absence of granules.
Chromophobes
- less numerous (10%)
- 4-5x more potent
- short acting (1/2 to 2 days)
Triiodothyronine (T3)
✓ Outermost layer
✓ Composed of cells arranged in irregular ovoid clusters separated by delicate fibrous trabeculae continuous with the fibro collagenous capsule.
✓ The cells have round nuclei and less cytoplasm than the cells in the zona
fasciculata
✓ The cytoplasm contains plentiful smooth endoplasmic reticulum and
mitochondria, but with only scanty lipid droplets
✓ Secretes mineralocorticoid hormones principally aldosterone.
Zona glomerulosa
- Hyposecretion of glucocorticoids and aldosterone causes Addison’s disease (chronic
adrenocortical insufficiency). - Symptoms, which typically do not appear until 90% of the adrenal cortex has been
destroyed, include mental lethargy, anorexia, nausea and vomiting, weight loss,
hypoglycemia, and muscular weakness. - Loss of aldosterone leads to elevated potassium and decreased sodium in the blood, low
blood pressure, dehydration, decreased cardiac output, arrhythmias, and even cardiac
ADDISON’S DISEASE
nodular toxic goiter
GRAVE’S DISEASE
✓ Middle and broadest of the 3 cortical layers
✓ Consists of narrow columns and cords of cells, often only one cell thick,
separated by fine strands of collagen and capillaries
✓ The cell cytoplasm is abundant and pale staining due to large number of lipid
droplets present; mitochondria and smooth endoplasmic reticulum are also abundant.
✓ Secretes glucocorticoid hormones mainly cortisol
✓ Secretes small amounts of androgenic sex hormones
Zona fasciculata
