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Main page | Structure | Departments | Department of Histology and Embryology | Materials for students | Modul 2 | THYROID GLAND. PARATHYROID GLAND. SUPRARENAL GLAND.

THYROID GLAND. PARATHYROID GLAND. SUPRARENAL GLAND.
THYROID GLAND.
  1. It is composed of: connective tissue capsule, connective tissue septa, LOBULES – space between septae. Lobule is composed of numerous follicles. Follicle – is vesicle with wall and cavity. Cavity contains colloid. Wall of follicle is composed of simple epithelium. It includes 2 types of parenchymal cells :a) follicular cells. It are epithelium, b) parafollicular cells (or C-cells). It are neuroendocrine cells.
  2.  Under NORMAL function of thyroid gland follicular cells are  simple CUBOIDAL epithelium. Under HYPOfunction of thyroid gland follicular cells are simple SQUAMOUS epithelium. Under HYPERfunction its  are simple COLUMNAR epithelium.
  3. Function of follicular cells –is secretion of 2 hormones: T3 (or triiodothyronine) and T4 (or thyroxine). It regulate basal metabolism.  Function of parafollicular cells –is secretion of hormone calcitonin. It lowers Ca concentration in blood.
  4. Embryonic origin for follicular cells- is endoderm of 1st-2nd pharyngeal pouches. For C-cells - is neural crest.
SUPRARENAL GLAND.
It is composed of : connective tissue capsule and 2 layers below the capsule :a)cortex and b) medulla.
  1. CORTEX is composed of: a) epithelial cords (parenchyma), b) sinusoidal capillaries. Epithelial cords are composed of cortical endocrine cells and form 3 concentically arranged zones.
  2. If in microslide epithelial cords are arch-shaped – it is zona glomerulosa.
  3. If in microslide radial epithelial cords locate- it is zona fasciculata.
  4. If in microslide anastomising epithelial cords - it is zona reticularis.
  5. Function of zona glomerulosa cells-is secretion of hormones mineralocorticoids. Main from its- is aldosteron. Function of zona  fasciculata cells- is secretion of hormones glucocorticoids. Main from its –is cortisol. Function of zona  reticularis  cells - is secretion of male and female sex hormones. Aldosteron stimulates Na-ions reabsorption in renal tubules. Cortisol stimulates gluconeogenesis, ATP synthesis, supresses inflammation and allergy, decreases immunoglobulins producrion.
Complication of treatment: glucocorticoids in children can cause accidental involution of thymus.
  1. MEDULLA is composed of: a) chromaffin cells (it is parenchyma. Belong to neuroendocrine cells), b) sinusoidal capillaries.
Chromaffin cells include 2 types:a) epinephrocytes, b) norepinephrocytes.
  1. Function: Epinephrocytes secrete hormone adrenalin, norepinephrocytes secrete hormone noradrenalin. Both hormones constrict arterioles and increase blood pressure, accelerate heart rate, hence, participate in stress.
  2. Embryonic origin for cortical endocrine cells - is visceral layer of splanchnic mesoderm. Embryonic origin for medullary chromaffin cells – is neural crest.
 
PARATHYROID GLAND.
  1. It is composed of: connective tissue capsule, septae extend from capsule, space between septae contains parenchyma. It presented by epithelial cords. Cords are composed of 2 cell types: a)chief cells (hormonally active), b) oxyphil cells.
  2. Function of chief cells – is secretion of parathyroid hormone (PTH). This hormone insreases concentration of Ca-ions in blood (it is antagonist for calcitonin).
  3. Embryonic origin for chief and oxyphil cells - is endoderm of 3rd-4th pharyngeal pouches.
Составитель – доцент В.В. Бондаренко.
 
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