LESSON 24 cortas

The pituitary gland is made up of the neurohypophysis (posterior lobe) and adenohypophysis (anterior lobe). The neurohypophysis derives from the neuroectoderm, and the adenohypophysis from the oral ectoderm (Rathke's pouch).

The adenohypophysis is made up of the pars distalis, pars intermedia, and pars tuberalis. Pars distalis is the most voluminous part and includes cells expressing growth hormone (GH), prolactin (PRL), corticotropic hormone (ACTH), and gonadotropin (LH and FSH).

The secretion from the adenohypophysis is regulated by the hypothalamus through hypothalamic releasing factors (GHRH and somatostatin).

<p>GH cells, also known as somatotropin-producing cells, are the most stable cell type in the distal part of the adenohypophysis. They have a spherical or ovoid shape, elongated or columnar, and are distributed throughout the gland in small groups or palisades. They predominate in the lateral portions of the gland and represent 35-45% of the total cells.</p> Signup and view all the answers

<p>PRL cells, also known as mamotropes or lactotropes, represent 35-50% of the cells in the distal part of the adenohypophysis and increase in number to 60% during lactation.</p> Signup and view all the answers

<p>The ultrastructural characteristics of the cells that produce pituitary hormones are similar as they are protein hormones and follow the Palade scheme.</p> Signup and view all the answers

<p>The GH hormone has anabolic activity as a stimulant of cell division, protein synthesis, growth, and galactopoiesis in ruminants.</p> Signup and view all the answers

<p>The pituitary gland is involved in regulating important functions for animal bodies, such as metabolism, growth, and reproduction.</p> Signup and view all the answers

<p>The pituitary gland measures 1 to 2 cm in size and is shaped like a sac, made up of the neurohypophysis (posterior lobe) and adenohypophysis (anterior lobe).</p> Signup and view all the answers

<p>The pituitary gland is located below the hypothalamus, connected by a stem or pedicle, and surrounded by a diaphragm sellae and a folding of the dura mater.</p> Signup and view all the answers

<p>GH cells have spherical or ovoid secretory granules, and their size is homogeneous, with an average between 300-400 nm.</p> Signup and view all the answers

<p>GHRH stimulates and somatostatin inhibits GH secretion.</p> Signup and view all the answers

<p>Hormones from the endocrine system are released by secretory epithelial cells into the circulatory system. They circulate through the bloodstream until they reach their target organ, where they will take effect.</p> Signup and view all the answers

<p>Hormones can be of three types depending on their composition: a) Proteins and polypeptides (insulin, glucagon, etc.), b) Steroids (cortisol, aldosterone, etc.), and c) Amines (epinephrine, norepinephrine, etc.)</p> Signup and view all the answers

<p>The main endocrine organs are the hypophysis, thyroid, parathyroid, adrenal, and pineal glands. These organs are composed of groups of secretory epithelial cells delimited by a highly vascularized fibrous stroma, reflecting their high metabolic activity and secretion pathway.</p> Signup and view all the answers

<p>Both the nervous and endocrine systems interact to modulate and coordinate the body's metabolic activity by maintaining a stable physiological state, called homeostasis. The endocrine system releases hormones into the bloodstream, while the nervous system transmits electrochemical signals to control physiological functions.</p> Signup and view all the answers

<p>The neurohypophysis is composed of axons, cytoplasmic processes of pituicytes, and Herring bodies. Specific techniques such as Gomori haematoxylin-phloxin-chromic and alum with haematoxylin are used to visualize its components. The parenchyma has light blue dyes, and in its core there are thick lumps stained with intense blue, called Herring bodies.</p> Signup and view all the answers

<p>Axons running through the neurohypophyseal parenchyma present lateral dilatations that are storage areas for the secretion granules of ADH and oxytocin, known as Herring bodies. The axons end in the synaptic bulb, and they do so as a dilatation related to the capillary walls. Pituicytes, which are distributed throughout the neurohypophysis, have a morphology similar to that of fibrous astrocytes and seem to contribute to the metabolism of neurosecretion processes.</p> Signup and view all the answers

<p>The neuropil of the neurohypophysis has an acidophilic background (axons and cytoplasmic processes of the pituicytes) with nuclei (of the pituicytes). This acidophilic background resembles the image of the neurohypophysis with the HE technique.</p> Signup and view all the answers

<p>Pituicytes are distributed throughout the neurohypophysis and present diverse morphology, predominantly similar to that of fibrous astrocytes (star shape). They are related to each other like a stellate reticulum between axons.</p> Signup and view all the answers

<p>Herring bodies are thick lumps stained with intense blue, found in the core of the neurohypophyseal parenchyma. They are storage areas for the secretion granules of ADH and oxytocin and are related to the axons that run through the neurohypophysis. These bodies end up secreting their content into the extracapillary spaces.</p> Signup and view all the answers

<p>The axons that run through the neurohypophysis present lateral dilatations that are storage areas for the secretion granules of ADH and oxytocin, known as Herring bodies. They end in the synaptic bulb, and they do so as a dilatation related to the capillary walls.</p> Signup and view all the answers

<p>These techniques stain the parenchyma with light blue dyes, and in its core, there are thick lumps stained with intense blue, called Herring bodies. These bodies are arranged in isolation or in clusters close to vascular endings.</p> Signup and view all the answers

<p>Although a clear interaction between axons and pituicytes in neurosecretion processes is not known, pituicytes, which are distributed throughout the neurohypophysis, seem to contribute to the metabolism of these processes. They are related to each other like a stellate reticulum between axons.</p> Signup and view all the answers

<p>LH and FSH cells in the adenohypophysis are rounded or elongated with an eccentric nucleus, have a well-developed RER and Golgi complex, and control reproductive function. Their secretion is stimulated by GnRH and inhibited by oestrogens and testosterone (LH) and oestrogens and inhibin (FSH).</p> Signup and view all the answers

<p>TSH cells, also called thyrotropes, are basophilic cells that are scarce (5%), have irregular or angular morphology, measure 12-14 µm, and have the smallest secretory granules (maximum diameter of 150 nm).</p> Signup and view all the answers

<p>ACTH cells, also known as corticotropin cells, have a homogeneous distribution, predominantly antero-medial, represent 7% to 10% of the cells in the distal part, measure 12 to 15 µm, and have a well-developed RER, a large Golgi complex, and secretory granules of homogeneous electron density. ACTH secretion is stimulated by CRH and stimulates the secretion of cortisol and androgens from the adrenal cortex.</p> Signup and view all the answers

<p>The secretory granules of PRL cells are the largest in adenohypophyseal cells, spherical in shape, highly electrodense, and have an average size between 375-450 nm. PRL secretion is influenced by external and internal factors, regulated by PRH and PIF.</p> Signup and view all the answers

<p>Follicle-stellate cells are 8 to 10 µm cells that do not stain with usual dyes but are seen with markers such as the S100 protein and cytokeratins. They have few organoids, support and maintain the hydroelectrolytic medium, and with age, join together to form aggregates.</p> Signup and view all the answers

<p>The pars intermedia of the anterior pituitary gland is adjacent to the neurohypophysis, has two types of cells: cells that express melanocyte-stimulating hormone (MSH) and cells that express cytokeratins.</p> Signup and view all the answers

<p>The neurohypophysis is a dependency of the endocrine neural tube and has three parts: the median eminence, infundibulum or infundibular stalk, and pars nervosa or neural lobe.</p> Signup and view all the answers

<p>The median eminence is a continuation of the hypothalamus, the infundibulum or infundibular stalk is a connecting structure, and the pars nervosa or neural lobe is a collection of nerve fibers.</p> Signup and view all the answers

<p>Herring bodies are storage sites for neurophysin and oxytocin or vasopressin in the axon terminals of the neurosecretory cells of the hypothalamus, and they play a role in the release of these hormones into the bloodstream.</p> Signup and view all the answers

<p>The pituitary gland is connected to the hypothalamus via the infundibulum, which allows for the passage of hormones released by the hypothalamus into the pituitary gland for further regulation of endocrine function.</p> Signup and view all the answers

<p>The cells in the distal part of the adenohypophysis include ACTH cells (corticotropin cells), LH and FSH cells (gonadotropic cells), and TSH cells (thyrotropes), each with specific functions related to the secretion of hormones and regulation of various physiological processes.</p> Signup and view all the answers

<p>The anterior pituitary gland plays a crucial role in the regulation of various endocrine functions by secreting hormones such as ACTH, LH, FSH, TSH, and PRL, which in turn regulate the activity of target endocrine glands and influence physiological processes such as growth, reproduction, and metabolism.</p> Signup and view all the answers