ANATOMY-ems hypothalamus & pituitary gland Novi Anantari, dr Anatomy Department-FK Unisba

HYPOTHALAMUS GLAND This region, located in the ventral diencephalons, just under the thalamus (hypo-, “under”), forming the floor and the ventral part of the walls of the third ventricle. The hypothalamus weighs about 4 grams . It contains the highest integrative centers of the ANS. The shallow hypothalamic sulcus on the wall of the third ventricle demarcates the hypothalamus from the thalamus. Anteriorly, the hypothalamus is limited by the lamina terminalis, medially by the third ventricle, laterally by the subthalamus, and posteriorly it is continous with the midbrain.

HYPOTHALAMUS GLAND

HYPOTHALAMUS GLAND The hypothalamus includes : The optic chiasm is located in the rostral portion of the hypothalamic floor. The tuber cinereum is the portion of the hypothalamic floor between the optic chiasm and the mammillary bodies; which is a funnel-shaped eminence The infundibulum, a collective term for the median eminence and the infundibular stalk or stalk of pituitary, extends ventrally from the tuber cinereum to the pars nervosa of the hypofisis

HYPOTHALAMUS GLAND the infundibular recess : evaginate lumen of the third ventricle. The median eminence (the highly vascularized floor of the hypothalamus) is a part of the tuber cinereum The mammillary bodies are paired spherical nuclei (paired white masses) located inferior to the gray matter of the hypothalamic floor, caudal to the tuber cinereum and rostral to the posterior perforated substance.

HYPOTHALAMUS GLAND The hypothalamus consists of 3 regions : The supraoptic region ostral; the suprachiasmatic nucleus, the supraoptic nucleus, the paraventricular nucleus, the anterior hypothalamic area, and the lateral hypothalamic area; The mammillary region, which is most caudal; containing the following strucrures : the mammillary nuclei and the posterior nucleus; The tuberal region; which contains the following structures : the dorsomedial nucleus, the ventromedial nucleus, the arcuate nucleus, and the lateral hypothalamic area.

HYPOTHALAMUS GLAND The supraoptic region (rostral) the suprachiasmatic nucleus, the supraoptic nucleus, the paraventricular nucleus, the anterior hypothalamic area, and the lateral hypothalamic area

HYPOTHALAMUS GLAND The preoptic area and hypothalamus regulate endocrine activity through 2 mechanism : directly, by secretion of neuroendocrine products into the general circulation through the vasculature of the posterior pituitary (neurohypofisis) indirectly, by secretion of releasing hormones into the local portal plexus, which drains into the blood vessels of the anterior pituitary (adenohypofisis).

PITUITARY GLAND

HUMAN HYPOTHALAMIC-PITUITARY UNIT

PITUITARY GLAND The Master Gland :produces hormones that control the activity of other endocrine glands It is a small gland located in the sella turcica (Turk's saddle) of the sphenoid bone of the skull, immediately inferior to the hypothalamus of the brain. The sphenoid bone serves as a protective cradle around the gland. A stalk or infundibulum attaches the gland to the hypothalamus. Hormones and regulatory molecules from the hypothalamus travel down a plexus of blood vessels in the infundibulum to reach the hypophysis.

PITUITARY GLAND Contains two lobes, the anterior and posterior lobes. The anterior lobe, the adenohypophysis or pars distalis, produce many hormones that target other endocrine glands The pars intermedia, separates the anterior and posterior pituitary. It produces, melanocyte stimulating hormone (MSH). The posterior lobe, the neurohypophysis or pars nervosa, does not produce hormones; The hypothalamus produces antidiuretic hormone (ADH) and oxytocin (OT) which pass down the infundibulum to enter the neurohypophysis for storage and release.The neurohypophysis consists of axons from hypothalamic neurons. The normal adult pituitary gland weighs between 0.4 and 0.8 gram.

HUMAN HYPOTHALAMIC-PITUITARY UNIT

Midsaggital Nuclear Magnetic Resonance scan of the brain of a normal woman

HYPOTHALAMIC-PITUITARY HORMONES Cells in the supraoptic and paraventricular nuclei of the hypothalamus produce the peptide hormones oxytocin and vasopressin (antidiuretic hormone), The peptide hormones are transported down the hypothalamo-hypophyseal tract and secreted from axon terminals directly into the systemic circulation in the posterior pituitary (neurohypophysis). Both hormones are produce initially as pro-hormones in neurons of the hypothalamic nuclei. Vasopressin stimulates water reabsorption by the kidney, and oxytocin stimulates uterine contraction and milk ejection.

Hypothalamic and pituitary hormones

HYPOTHALAMIC-PITUITARY HORMONES Cells in the hypothalamus also control the anterior pituitary. Cells in a number of nuclei including the arcuate nucleus and part of the ventromedial nucleus produce peptide-releasing hormones Peptide Releasing Hormones are transported to their terminals and secreted into capillaries in the median eminence and pituitary stalk. These capillaries collect into very short portal veins that deliver the releasing hormones to cells of the anterior pituitary (adenohypophysis).

PITUITARY HORMONES Subpopulations of cells of the anterior pituitary synthesize and secrete : Thyroid-stimulating hormone, Follicle-stimulating hormone, Luteinizing hormone, Growth hormone, Adrenocorticotropic hormone, Prolactin.

HYPOTHALAMIC-PITUITARY CIRCULATION The blood supply reaches the anterior pituitary by a circuitous route through the hypothalamus. Two derivatives of the internal carotid arteries, the superior hypophyseal arteries (SHA), branch in the subarachnoid space around the pituitary stalk and terminate in the capillary network of the median eminence. These capillaries have a fenestrated endothelium which allows easy access to the hypothalamic releasing hormones.

HYPOTHALAMIC-PITUITARY CIRCULATION Transport of substances from the capillaries to the median eminence is also facilitated because the median eminence lies outside the blood-brain barrier. The capillaries then coalesce to form 6 to 10 straight veins known as the hypothalamic-pituitary portal circulation. These veins constitute the main blood supply to the anterior lobe and supply it with nutrients as well as information from the hypothalamus. A direct arterial blood supply the anterior lobe is also present. The posterior pituitary is supplied entirely from the inferior hypophyseal arteries.

Hormones of the hypothalamic anterior pituitary pathway

A complex endocrine pathway