The Basic Anatomy of the Endocrine System
The first part of the Endocrine system is the Hypothalamus. The Hypothalamus is a part of the brain , that is superior and anterior to the brain stem and inferior to the thalamus. It has many different jobs, serving the body’s nervous system. It is also responsible fro controlling the endocrine system directly through the pituitary gland. The hypothalamus also contains special neurosecretory cells that secrete hormones.
There are several:
- Growth hormone-releasing hormone (GHRH)
- Thyrotropin-releasing hormone (TRH)
- Growth hormone-inhibiting hormone (GHIH)
- Corticotropin-releasing hormone (CRH)
- Antidiuretic hormone (ADH)
- Gonadotropin-releasing hormone (GnRH)
These inhibiting and releasing hormones will affect the anterior pituitary gland. Anterior pituitary gland is stimulated by TRH, causing the gland to release thyroid-stimulating hormones. GHRH releases and GHIH will inhibit the release growth hormone. GnRH stimulate follicle release and luteinizing hormones, while CRH stiles the release of adrenocorticotropic hormones. Oxytocin and antidiuretic hormones are produced by the hypothalamus and sent to the posterior pituitary gland and stored for future release.
The Pituitary Gland:
The pituitary gland is also the hypophysis, which is a small pea-sized lump of tissue that is on the back portion of the hypothalamus of the brain. In-fact many of the blood vessels that are around the pituitary gland move hormones throughout the body. This small depression in the spheroid is the sella turcica. There are two completely different structures in the pituitary gland. The Posterior and anterior pituitary gland.
1. The Posterior Pituitary gland is a not a glandular tissue, but a nervous tissue. It is a small extension of the hypothalamus and inside the axons of some of the neuroscretory cells of hypothalamus also extend. The neurosecretory cells create 2 different hormones in the hypothalamus, which are stored in the posterior pituitary gland for later release.
- In women, the oxytocin hormone triggers the uterine to contract during childbirth and and release milk for breastfeeding.
- The Antidiuertic hormone (ADH) will prevent the water loss in the body by increasing the kidney’s water intake and reduce the blood flowing to sweat glands.
2. Anterior Pituitary glands are made of glandular tissue. The anterior pituitary gland can release and inhibit hormones of the hypothalamus. The anterior pituitary gland will produce six vital hormones:
- Thyroid stimulate hormone (TSH) is a tropic hormone that will stimulate the thyroid gland.
- The Follicle stimulate hormone or (FSH) stimulates the body’s follicle cells of the gonads and produce gametes, which is sperm in males and ova in females.
- TheAdrenocorticotropic hormone (ACTH) stimulates the adrenal cortex ,which is outside the adrenal gland.
- Luteinizing hormones (LH) will stimulate the gonads that produce sex hormones such as estrogen in females and testosterone in males.
- Human growth hormones (HGH) will affect targeted cells in the body to stimulate their reproduction, repair and growth.
- The Prolactin (PRL) hormones do multiple things through the body, and effects many parts, mainly stimulating the mammary glands in breast to produce milk in females.
The pineal gland is quite small, mass of glandular tissue, and have the shape of a pinecone. This is found in the posterior region of the thalamus. The pineal gland will produce the melatonin hormone that regulates the body’s circadian rhythm, also known as the sleep-wake cycle. The retina’s photoreceptors inhibits stimulation to the pineal gland. Melatonin produce in low light or darkness, from the sensitivity of light. When the pineal gland becomes active when the body begins to produces more melatonin, the body will feel drowsy at night time.
The Thyroid Gland
The thyroid gland is shaped like a butterfly. It is at the bottom of the neck and wraps around the lateral sides of the trachea. The thyroid gland produces 3 important hormones such as:
- Triiodothyronine (T#)
- Thyroxine (T4)
The Calcitonin gets released when calcium ion levels in the blood increase above a set position. By aiding the absorption of calcium into the bods, calcitonin reduces the concentration of calcium ions inside the blood. Triiodothyronine and Thyroxine hormones work to regulate the body’s metabolic rate. With higher levels of T3 and T4 can cause growing cellular activity and energy usage.
Parathyroid glands consist of four small masses of glandular tissue which are in the posterior side of the thyroid gland. The parathyroid glands create the hormone parathyroid hormone (PTH), that are involved in calcium ion homeostasis. When calcium levels are lower than a set point in the blood, PTH releases parathyroid glands. PTH stimulates osteoclast to break down calcium containing the bone matrix, releasing calcium ions form the bloodstream. PTH triggers kidneys to return calcium ions filtered out the blood back into the bloodstream.
Adrenal glands are a triangular shaped glands that are superior to the body’s kidneys. This are two different and unique layers. They both have their own functions. The other layer is the adrenal cortex and the inner layer is the adrenal medulla.
The adrenal cortex: creates many of the cortical hormones in three different classes:glucocorticoids, mineralocorticoids, and androgens.
- Glucocorticoids have many different functions. They can breakdown lips and proteins to develop glucose. Glucocorticoids also decrease the amount of inflammation and immune the responses.
- Mineralocorticoids are responsible for hormones that regulate the concentration of ion minerals inside the body.
- Androgens, like testosterone are created a low levels in the adrenal cortex, that help guide the development and growth activity of cells that are receptive to male hormones. Adult men produce many times higher the amount of androgens in the testes than in the adrenal cortex, this is what creates the appearance of male secondary sex characteristics.
The Pancreas, located in the abdominal cavity, inferior and posterior to the stomach, is a large gland. The pancreas is thought to be the a heterocrine gland because it contains exocrine and endocrine tissue. The endocrine cells make up only 1% of the pancreas total mass. Endocrine cells are found in small sections within the pancreas called islets of Langerhans. Inside the islets there are two types of cell. These are alpha and beta cells. Alpha cells creates the glucagon hormone, which raises blood glucose levels. Glucagon initiates certain liver and muscle cells to break down polysaccharide glycogen to release glucose into the bloodstream. Beta cells create the insulin hormone, that lowers the blood glucose level after eating meal. The insulin will initiate the absorbing of glucose form blood into the cells, which are added into glycogen molecules for storing.
Gonads are different in women and men. In females the gonads are the ovaries and males testes are the gonads. They both are responsible for creating sex hormones for the body. These sex hormones determine the secondary sex characters for adult males and females.
The testes are a pair of ellipsoid organs that are located in the male scrotum. They produce androgen testosterone in males after they begin puberty. Testosterone effects many different parts of the body. including bones, muscles, sex organs and the hair follicles. Hormones will trigger growth and increase strength and mass in the muscles and bones, as well as accelerating the growth of long bones during the males adolescence. During puberty the testosterone will control the development of hair for males, including pubic, chest, back, legs, and facial hair. Men who inherited genes for baldness testosterone will cause onset of androgenic alopecia or male pattern baldness during this time.
Ovaries are two almond shaped glands that are found in the pelvic body cavity superior and lateral of the uterus in females. The ovaries create female sex hormones estrogen and progesterone. Estrogen are a group of hormones that are released during puberty and triggers the development secondary sex characteristics such as uterine development, breast growth and pubic hair. Estrogen also causes increase bone growth during the adolescence period.Progesterone is active during ovulation and pregnancy in females e and maintains the conditions so that females scan support development of the fetus.
The thymus is a soft organ shaped like a triangle, found on the chest posterior of the sternum. The thymus regulates the hormones called thymosins that help guide and create T-lymphocytes during the fetal development phase and childhood. T-lymphocytes, developed in the thymus go on to guard the body from pathogens for the rest of a person’s life. The thymus becomes inactive during puberty and replace with adipose tissue throughout the person’s life.