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THYROID GLAND. PARATHYROID GLAND. SUPRARENAL GLAND.
THYROID GLAND.
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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.
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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.
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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.
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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.
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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.
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If in microslide epithelial cords are arch-shaped – it is zona glomerulosa.
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If in microslide radial epithelial cords locate- it is zona fasciculata.
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If in microslide anastomising epithelial cords - it is zona reticularis.
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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.
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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.
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Function: Epinephrocytes secrete hormone adrenalin, norepinephrocytes secrete hormone noradrenalin. Both hormones constrict arterioles and increase blood pressure, accelerate heart rate, hence, participate in stress.
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Embryonic origin for cortical endocrine cells - is visceral layer of splanchnic mesoderm. Embryonic origin for medullary chromaffin cells – is neural crest.
PARATHYROID GLAND.
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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.
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Function of chief cells – is secretion of parathyroid hormone (PTH). This hormone insreases concentration of Ca-ions in blood (it is antagonist for calcitonin).
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Embryonic origin for chief and oxyphil cells - is endoderm of 3rd-4th pharyngeal pouches.
Составитель – доцент В.В. Бондаренко.
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