To study the endocrine system using specimens, models
To study the endocrine system using specimens, models etc.
Requirements: Specimen, models, charts, etc. of various endocrine organs.
Study of Endocrine Glands: The following method should be followed to study an endocrine gland:
b) Division or parts
d) Blood supply
e) Nerve supply
a) Hormones secreted by the glands
b) Actions of each hormone
Study of Endocrine Disorders: The endocrine disorder is studied by analyzing.
b) Signs and symptoms
c) Syndrome (combination of signs and symptoms suggesting the presence of disease).
Hormones of Hypothalamus
The hormones are summarized as follows :
(a) Adrenocorticotropic releasing hormone (ARH) stimulates the anterior lobe of the pituitary gland to secrete its adrenocorticotropic hormone (ACTH).
(b) Thyrotropic releasing hormone (TRH) stimulates the anterior lobe of the pituitary gland to secrete its thyroid stimulation hormone(TSH) or thyrotropin.
(c) Somatotropin releasing hormone (GIH) or somatostatin (SS) stimulates the anterior lobe of the pituitary gland to release growth hormone (HGH) or somatotropin.
(d) Growth inhibiting hormone(GIH) or somatostatin (SS) inhibits the secretion of hGH from the anterior lobe of the pituitary gland.
(e) Gonadotropin-releasing hormone (GnRH) stimulates the anterior lobe of the pituitary gland to secrete two gonadotropic hormones: follicle-stimulating hormone(FSH) and luteinizing hormone (LH).
(f) Prolactin releasing hormone (PRH) stimulate the anterior lobe of the pituitary gland to secrete its prolactin.
(g) Prolactin inhibiting hormone (PIH) inhibits the secretion of prolactin from the anterior lobe of the pituitary gland.
(h) Melanocyte-releasing hormone(MRH) stimulates the intermediate lobe of the pituitary gland to secrete its melanocyte-stimulating hormone (MSH).
(i) Melanocyte inhibiting hormone(MIH) inhibits the secretion of melanocyte-stimulating hormone from the intermediate lobe of the pituitary gland.
I. PITUITARY GLAND (HYPOPHYSIS cerebri): MASTER GLAND Anatomy
It develops from the ectoderm of the embryo. This pear-shaped gland measuring 1-.5 cm in diameter lies in the hypophyseal fossa of sella turcica of the sphenoid bone. It attaches to the hypothalamus by a stalk, the infundibulum, and has two anatomically and functionally separate lobes. The anterior pituitary (anterior lobe), also called the adeno hypophysis form 75% of the total weight of the gland. It consists of two parts in an adult the pars distails is the larger portion, and the pars tuberalis form a sheath around the infundibulum. The posterior pituitary(posterior lobe), also called the neurohypophysis, consists of two parts –the pars nervosa (larger bulbar portion) and the infundibulum.
Adenohyphysis originates as Rathke’s pouch from the dorsal wall of the stomodaeum in the embryo, but later its connection with the stomodaeum disappears. The neurohypophysis originates as an outgrowth from the floor of the diencephalon. Thus, the pituitary gland is dual in origin. A third lobe called pars intermedia (intermediate lobe) atrophies during foetal development, but it migrates into adjacent parts of the anterior pituitary, where they persist.
II THYROID GLAND
The thyroid gland is the largest endocrine gland (normal mass 30 g) located anterior to the thyroid cartilage of the larynx in the neck. It develops from the endoderm of the embryo. It is highly vascularized and receives 80-120 ml of blood per minute. It is composed of the right and left lateral lobes one on either side of the trachea, that are connected by an isthmus.
Microscopic spherical sacs are called thyroid follicles to make up most of the thyroid gland. The wall of each follicle consists of cuboidal follicular cells (thickness increases or decreases when they are active or inactive). The follicles are filled with a homogeneous material called colloid. A small amount of loose connective tissue forms the stroma of the gland. Besides containing blood capillaries, the stroma contains small clusters of specialized parafollicular cells or ‘C’ cells. The thyroid gland can store enough hormones in the colloid to supply the body for about 2 months.
The follicular cells produce two hormones: thyroxine or tetraiodothyronine(T4), and triiodothyronine (T3). T3 and T4 are also known as thyroid hormones (TH). Parafollicular (or C) cells produce the hormone calcitonin, which helps to regulate calcium homeostasis. The thyroid gland is stimulated to release its hormones by thyroid-stimulating hormone (TSH) or thyrotropin secreted by the anterior lobe of the pituitary. Their secretion is controlled by a negative feedback system.
III PARATHYROID GLANDS
They develop from the endoderm of the embryo and consist of four separate glands located on the posterior surface of the lobes of thyroid glands. Each has a mass of about 40mg. Usually, one superior and one inferior pair of parathyroid glands are attached to each lateral thyroid lobe.
V ADRENAL (SUPRARENAL) GLANDS- GLANDS OF EMERGENCY
The adrenal cortex is derived from the mesoderm of the embryo and the adrenal medulla develops from the neuroectoderm of the embryo.
These are paired structures located on the top of kidneys and have a flattened pyramidal shape (Figure 3.5) In an adult, each gland is 5.5 cm in height, 2.3 cm in width and a little less than 1 cm thick, with a mass of 3.5-5 g (half its size at birth). During embryonic development, the adrenal glands differentiate into two structurally and functionally distinct regions: A large, peripheral adrenal cortex (80- 90% of the gland) and a small, centrally located adrenal medulla. A connective tissue capsule covers the gland. The adrenal glands are highly vascularised.
VI Pineal Gland (Eplphysiss Cerebral)
It develops from the ectoderm of the embryo. It is a small pinecone-shaped endocrine gland attached to the roof of the third verticle of the brain at the midline. Part of the epithalamus, it is positioned between the two colliculi. The gland consists of masses of neuroglia and secretory cells called pinealocytes.
VII THYMUS GLAND
It is derived from the endoderm of the embryo. The thymus is located behind the sternum between the lungs (Figure 3.7). It is the soft, pinkish, bilobed mass of lymphoid tissue. It is a prominent gland at the time of birth but gradually atrophies in the adult. An enveloping layer of connective tissue holds the two lobes closely together, but a connective tissue capsule separates the two. Extensions of the capsule, called trabeculae, penetrate inward and divide each lobe into lobules. Each lobule consists of an outer cortex and a central medulla.
VIII PANCREATIC ISLETS
The pancreas is derived from the endoderm of the embryo and is both an endocrine gland and an exocrine gland. Only its endocrine functions will be discussed here. This flattened organ measures about 12.5-15 cm in length and is located in the curve of the duodenum. It consists of a head, a body and a tail. About 99% of pancreatic cells are arranged in clusters called acini. The acini produce digestive enzymes, which flow into the gastrointestinal tract of endocrine tissue called pancreatic islets or islets of Langerhans. Abundant capillaries serve both the exocrine and endocrine portions of the pancreas.
IX. GONADS (OVARIES AND TESTES)
Gonads develop from the mesoderm of the embryo and are organs that produce gametes- sperms in males and oocytes in females. They also secrete hormones.
These are paired oval bodies located in the female pelvic cavity in close proximity to the oviducts and the uterus. Ovaries secrete estrogens, progesterone, relaxin and inhibin/ actin.
(i) Estrogens (Estradiol and Estrone): These are secreted by the cells of Graafian follicles and stimulate the development of female secondary sex characteristics during puberty and maintain them through the reproductive years of adult life. They also stimulate the maturation of ova and the development of the uterine epithelium and the mammary glands.
(ii) Progesterone: This secretion of the corpus luteum stimulates further development of the uterine epithelium and mammary glands. It is also required for the formation of the placenta and for the maintenance of pregnancy. It is also required for ovulation along with estradiol.
(iii) Relaxin; It is produced by the corpus luteum during the later stages of pregnancy and helps to soften ligaments that hold the public symphysis together. It may also affect other ligaments, e.g., foot ligaments causing an increase in shoe size following pregnancy, and helps dilate the uterine cervix during labour and delivery.
(iv) Inhibin/ Action : Inhibin/ actin is secreted by the corpus luteum. Inhibin, a protein hormone, inhibits and actin hormone activates the FSH and GnRH production.
A pair of testes, the male gonads, are oval glands that lie in the scrotum. The connective tissue present between the seminiferous tubules in a testis contains small clusters of endocrine cells called interstitial cells or Leydig’s cells. The main hormone secreted by these cells is testosterone, an androgen or male sex hormone.
(i) Functions of Testosterone: It stimulates descent of testes before birth, regulates spermatogenesis, and promotes the development and maintenance of secondary sex characteristics (e.g., beard, moustache, and low-pitch male voice), growth of bones and muscles, etc.
(ii) Inhibin/ Actin: It is secreted by sustentacular (supporting) cells of the seminiferous tubules of the testes. Inhibin hormone inhibits and actin hormone activates the secretion of FSH from the anterior pituitary.
BP207P Human Anatomy and Physiology II Practical
To study the integumentary and special senses using specimens, models, etc.,
To study the nervous system using specimens, models, etc.,
To study the endocrine system using specimens, models, etc
To demonstrate the general neurological examination
To demonstrate the function of olfactory nerve
To examine the different types of taste.
To demonstrate the visual acuity
To demonstrate the reflex activity
Recording of body temperature
Determination of tidal volume and vital capacity.
Study of digestive, respiratory, cardiovascular systems, urinary and reproductive systems with the help of models, charts and specimens.
Recording of the basal mass index.
Study of family planning devices and pregnancy diagnosis test.
Demonstration of total blood count by cell analyzer
Permanent slides of vital organs and gonads
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