Presentation on theme: "Endocrine System Department of Histology and Embryology Zhang Xi-mei."— Presentation transcript:
1Endocrine SystemDepartment of Histologyand EmbryologyZhang Xi-mei
2Introduction Composition: Endocrine glands (thyroid, parathyroid, adrenal gland, hypophysis ,and pineal body)Endocrine cell massEndocrine cellsFunction:Regulate the activities of various cells, tissues, and organs in the body.Maintain homeostasis and coordinate body growth and development.
3Characteristics of endocrine glands Cells are arranged in cord, follicle, aggregation or net-like structure.Ductless.Contain rich blood vessels. The endocrine cells are always close to the capillaries, which receive the secreted hormones.
4ThyroidLocate in the cervical region anterior to the larynx,consists of two lobes united by an isthmus.Its function is to synthesize the hormones thyroxine (T4)and triiodothyronine(T3).
5ThyroidIt is composed of thyroid follicles. The follicles are lined by a simple cuboidal epithelium.The central cavity contains a gelatinous substance called colloid, which is composed of thyroglobulin.
7Follicular cellsThey are responsible for production of thyroxine (T4)and triiodothyronine(T3).Major function of T4 and T3Regulate growth and development: most cells require T3/T4 for growth. The nervous system is especially sensitive.Calorigenic effect: T3/T4 increase basal metabolic rate (BMR) and affect temperature regulation.Cardiovascular effects: increase heart rate.
8Parafollicular cells (C cells) Locate in the follicular epithelium or as isolated among thyroid follicles.Larger than follicular cells and less stained.Secrete calcitonin, which can decrease the blood Ca2+ level by inhibiting the activity of osteoclasts.
9ParathyroidFour small glands.Located behind the thyroid gland.
10Structure Cells are arranged in cords. Chief cells (principal cells) Oxyphil cells
11Chief cells More numerous. Secretory granules in the cytoplasm (contain parathyroid hormones, PTH), which can increase the blood Ca2+ level.PTH and calcitonin have reciprocal effects in the regulation of blood calcium level .
12Oxyphil cellsLarger than chief cells, contains many acidophilic granules (mitochondria).The function is unknown.
13They are paired organs lie near the superior poles of the kidneys. They are flattened structures with a half-moon shape.
14Adrenal glandCortex: located in the periphery. It is the steroid-secreting portion.Medulla: located in the center. It is the catecholamine-secreting portion.
15Adrenal gland Cortex: it is divided into 3 zones : Zona glomerulosa (15%)Zona fasciculata (80%)Zona reticularis (5%)
16Zona glomerulosa It is the narrow outer zone. The cells are arranged in closely packed, rounded, or arched cords.The cells secrete mineralocorticoid (aldosterone).Aldosterone acts on the distal tubules of the kidney,and the gastric mucosa to stimulate the resorption of sodium by the epithelial cells.
17Zona fasciculata Arranged in one-or two- cell thick straight cords. A great number of lipid droplets in the cytoplasm.Secrete glucocorticoid (cortisol).Promote normal metabolism, particularly carbohydrate metabolism, which increases blood glucose levels.Suppress the immune response by destroying circulating lymphocytes.
18Zona reticularis It lies between the zona fasciculata and the medulla. It contains cells disposed in irregular cords that form network.It secrete gonadocorticoids or sex hormones, influences the sexual development.
19Adrenal medulla Chromaffin cells (medullary cells). They have abundant granules in the cytoplasm.Epinephrine-secreting cells and norepinephrine-secreting cells secrete epinephrine and norepinephrine, respectively.These two hormones are secreted in response to stimulation by sympathetic nerve, particularly during stressful situations.
24Cells of Adenohypophysis Somatotropic cellThey produce growth hormone (GH, somatotropin) which can stimulates growth, stimulates growth of long bone, muscular and skeletal development.Mammotropic cellThey produce prolactin (PRL) which promotes mammary gland development, initiates milk formation.
25Thyrotropic cellThey produce Thyroid-Stimulating Hormone (TSH), or thyrotropin. It stimulates thyroid hormone synthesis, storage and liberation.Gonadotropic cellThey secrete Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH).In females, FSH promotes follicle development and secretion of estrogens.In males, FSH stimulates the maturation of developing sperm.In females, LH promotes ovarian follicle maturation and progesterone secretion.In males, LH is essential for maintenance of androgen secretion.Corticotropic cellThey produce adrenocorticotropic hormone (ACTH), or corticotropin, which stimulates the release of the adrenal cortex.
26Pars tuberalis Pars intermedia It is a funnel-shaped region surrounding the infundibulum of the neurohypophysis.Most of the cells in the Pars tuberalis secrete gonadotropins.Pars intermediaContains follicles.Functions unknown.
27Neurohypophysispars nervosa is composed of unmyelinated axons of neurosecretory neurons, whose cell bodies locate in paraventricular and supraoptic nuclei in hypothalamusInfundibulum (Composed of median eminence and neural stalk).Herring bodies: the axon dilations in pars nervosa come from neurosecretory neurons, are light acidophilic and contain many secretory granules (antidiuretic hormone, ADH and oxytocin, OCT).
28Major function of ADHThe antidiuretic hormone (ADH, vasopressin), which is produced by supraoptic nuclei, promote water reabsorption in kidney.In large dose, ADH also stimulates the contractions of smooth muscle of small arteries and arterioles.Major function of OxytocinOxytocin is synthesized by paraventricular nuclei in the hypothalamus and is stored in the neurohypophysis.In the uterus, oxytocin stimulates the contraction of the uterus in order to deliver the fetus. In the mammary glands, oxytocin also stimulates the ejection of milk when infants suckle.
29Homework Describe the secretory cells of the pars distalis. Herring bodies.Parafollicular cells.Describe the structure and function of adrenal gland.