Endocrine System Anatomy Quiz

The endocrine system is one of two major control systems in the body, the other being the nervous system. It regulates body function through the production and release of hormones, which are transported through the bloodstream to target organs. Hormones act slowly, taking minutes to days to exert their effects, and operate at low concentrations.

Endocrine glands are ductless, meaning they release hormones directly into the bloodstream without using ducts to transport secretions.

Endocrine glands have specialized cells organized into structures like columns, glomeruli, follicles, or groups, with at least one surface facing a blood capillary. This arrangement allows efficient release of hormones into the bloodstream.

Endocrine glands are richly supplied with fenestrated capillaries, which have large pores allowing for easy passage of hormones into the bloodstream.

The Pituitary gland, also known as the hypophysis cerebri, is located at the base of the skull, tucked into a bony depression called the sella turcica.

The Pituitary gland has a front lobe called the anterior pituitary (adenohypophysis) and a back lobe called the posterior pituitary (neurohypophysis).

The anterior pituitary lobe consists of three parts: the pars distalis, pars tuberalis, and pars intermedia.

The pars distalis is the largest part of the anterior pituitary and plays a crucial role in hormone synthesis and secretion.

A region in the anterior pituitary that consists of basophils and contains colloid-filled cysts. It is located between the pars distalis and pars nervosa.

Cells in the pars distalis of the anterior pituitary that stain with acidic dyes. They have granular cytoplasm and include somatotrophs, lactotrophs, corticotrophs, and gonadotrophs.

Cells in the pars distalis of the anterior pituitary that do not stain readily with common histological stains. They have smaller size and non-granular cytoplasm compared to chromophils.

Cells in the pars distalis that secrete growth hormone (GH) responsible for growth and development.

Cells in the pars distalis that secrete prolactin, hormone responsible for milk production in females.

Unmyelinated axons of magnocellular neurosecretory cells present in the supraoptic and paraventricular nuclei of the hypothalamus. They traverse through the infundibulum and reach the posterior lobe.

The posterior lobe of the pituitary gland composed of fibers and cells.

The stalk that connects the pituitary gland to the hypothalamus.

A specialized blood vessel system that connects the hypothalamus to the anterior pituitary, allowing for the transport of hypothalamic hormones to regulate hormone secretion in the pituitary.

A network of nerve fibers that connects the hypothalamus to the posterior pituitary, allowing for the transport of hypothalamic hormones directly into the bloodstream.

Antidiuretic hormone (ADH) and oxytocin are synthesized by large neurons in the supraoptic and paraventricular nuclei, respectively. They are then transported down axons of the hypothalamic-hypophyseal tract and released into the bloodstream from the posterior pituitary.

Hormones produced by the hypothalamus that regulate hormone secretion in the anterior pituitary. They are released from axons in the median eminence and transported through the portal system to the anterior pituitary.

Hormones secreted by the anterior pituitary, like growth hormone, that play roles in various bodily functions.

The pineal gland is located in the brain, shaped like a pine cone.

The pineal gland develops from the same embryonic tissue as the brain.

Dilated areas along the axons of the hypothalamic-hypophyseal tract where hormones are stored in the posterior pituitary. They appear as faintly basophilic structures under a microscope.

Specialized glial cells found in the posterior pituitary that support the neurons and their axons carrying hormones.

Hormones released by the posterior pituitary: ADH (Antidiuretic Hormone) regulates water reabsorption and oxytocin is involved in uterine contractions and milk release.

ADH is released in response to increased blood tonicity, sensed by osmoreceptors in the hypothalamus. It increases permeability of renal collecting ducts to water, promoting water reabsorption and regulating osmotic balance.

The superior hypophyseal arteries supply the median eminence and the infundibular stalk.

The inferior hypophyseal arteries provide blood mainly for the neurohypophysis (posterior pituitary).

A network of capillaries found in the median eminence and infundibular stalk that allow exchange of substances between the hypothalamus and the pituitary.

The pineal gland, located in the brain, has a unique structure with secretory cells called pinealocytes and calcified structures called corpora arenacea. The gland is enclosed by connective tissue and separated into lobules by septa containing blood vessels, creating a distinct organization.

Pinealocytes, the main cell type in the pineal gland, have abundant mitochondria, secretory vesicles, and long cytoplasmic processes that extend toward blood capillaries, indicating an endocrine function. They synthesize and release melatonin, a hormone derived from tryptophan.

The pineal gland receives unmyelinated sympathetic nerve fibers that synapse with pinealocytes. The gland also contains interstitial glial cells, similar to astrocytes, which support and regulate the environment of the pinealocytes.

Melatonin, a hormone produced by the pineal gland, is influenced by light and darkness. Darkness promotes melatonin release, whereas daylight inhibits it. This creates a daily rhythm in blood melatonin levels.

The rhythmic changes in blood melatonin levels have a significant impact on the hypothalamus, pituitary gland, and other endocrine tissues, contributing to the 24-hour (circadian) rhythm of physiological functions and behaviors.

Light and darkness signals are detected by the retina and transmitted to the pineal gland via the retinohypothalamic tract, suprachiasmatic nucleus, and sympathetic nerve pathways. The pineal gland serves as a transducer, converting light signals into hormonal changes.

The pineal gland plays a crucial role in regulating the circadian rhythm of physiological functions and behaviors, influencing endocrine activity and contributing to sleep-wake cycles and other daily rhythms.

Corpora arenacea are calcium and magnesium salt concretions found in the pineal gland. These structures increase in number and size with age but have no known effect on the gland's function.