Pituitary gland ANATOMY /MD

Objectives Embryology Introduction Anatomy of pituitary gland Pituitary gland secretions Vascular supply of pituitary gland

Embryology

Introduction & anatomy called the hypophesis, sometimes called the master gland and its endocrine gland Measures about 1 centimeter in diameter and 0.5 to 1 gram in weight Lies in the sella turcica, connected to the hypothalamus by the pituitary/ hypophysial stalk. Physiologically, divided into two distinct portions: 1. Anterior pituitary (Adenohypophysis) 2. Posterior pituitary (Neurohypophysis) Between these is a small, relatively avascular zone called the pars intermedia ,Almost absent in the human being but is much larger and much more functional in some lower animals

Anterior Pituitary (Adenohypophysis) Anterior pituitary consists of three parts: 1. Pars distalis 2. Pars tuberalis 3. Pars intermedia Anterior pituitary has two types of cells, which have different staining properties: 1. Chromophobe cells 2. Chromophil cells

The pars distalis contains two types of cells including chromophobe cells and chromophil cells. Chromophobe Are not secretory in nature, but are the precursors of chromophil cells. The chromophils can be further divided into acidophils (alpha cells) and basophils (beta cells). These cells all together produce hormones of the anterior pituitary, and release them into the blood stream.

Hormones that secrets by anterior lobe Growth hormone. Growth hormone regulates growth and physical development. It can stimulate growth in almost all of your tissues. Its primary targets are bones and muscles. Thyroid-stimulating hormone. This hormone  activates your thyroid to release thyroid hormones. Your thyroid gland and the hormones it produces are crucial for metabolism. Adrenocorticotropic hormone. This hormone stimulates your adrenal glands to produce cortisol and other hormones. Follicle-stimulating hormone. follicle stimulating hormone is involved with estrogen secretion and the growth of egg cells in women. It’s also important for sperm cell production in men. Luteinizing hormone.leuteinzing is involved in the production of estrogen in women and testosterone in men. Prolactin. prolactin helps women who are breastfeeding produce milk. Endorphins. endophins have pain-relieving properties and are thought to be connected to the “pleasure centers” of the brain. Enkephalins. Enkephalins are closely related to endorphins and have similar pain-relieving effects. Beta-melanocyte-stimulating hormone. This hormone helps to stimulate increased pigmentation of your skin in response to exposure to ultraviolet radiation. Its precursor is (proopiomelanocortin) and sometimes its called secreted from The intermediate lobe

mnemonics for the hormones secreted by the anterior pituitary gland (FLAT PIG) F- FSH L- LH A- ACTH T- TSH P- Prolactin G- GH actually, make it FLAT PEG and add E for Endorphins (according to the kaplan book)

Posterior pituitary (Neurohypophysis) Bodies of the cells that secrete the posterior pituitary hormones are not located in the pituitary gland. Large neurons, called magnocellular neurons, located in the supraoptic and paraventricular nuclei of the hypothalamus synthesise post pitutary hormones. roject axons down the infundibulum to terminals in the posterior pituitary.   hormones are usually produced in your hypothalamus and stored in the posterior lobe until they’re released.

Hormones stored in the posterior lobe include: Vasopressin.(ADH) This is also called antidiuretic hormone . It helps your body conserve water and prevent dehydration. Oxytocin. This hormone stimulates the release of breast milk. It also stimulates contractions of the uterus during labor.

Vascular supply of pituitary gland The vasculature of the pituitary gland is complex and unique. Whilst the anterior lobe and posterior lobe have the same venous drainage (anterior and posterior hypophyseal veins), they have an individual arterial supply: Anterior Pituitary The anterior pituitary gland receives arterial supply from the superior hypophyseal artery (a branch of the internal carotid artery). This vessel first forms a capillary network around the hypothalamus – blood from this network is then transported to a secondary capillary plexus surrounding the anterior pituitary. Known as the hypothalamo-hypophysial portal system, this structure allows the hypothalamus to communicate with the anterior pituitary via the release of neurotransmitters into the bloodstream. Posterior Pituitary The infundibulum and posterior pituitary gland receive a rich blood supply from many arteries. Of these, the major vessels are the superior hypophyseal artery, infundibular artery and inferior hypophyseal artery. Veins drains into ( inter cavernous sinus )

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