Pituitary Gland Functions and Structure

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Questions and Answers

What is the primary function of the growth hormone in the body?

Mediating growth and metabolic functions (correct)

Enhancing the immune response

Stimulating the production of red blood cells

Regulating calcium levels in the blood

Which of the following statements correctly describes the anterior pituitary?

It is an avascular structure.

It arises from pharyngeal epithelium as Rathke's pouch. (correct)

It is directly responsible for regulating the secretion of thyroid hormones.

It develops from the neuroectoderm.

How is growth hormone secretion regulated?

It is primarily based on genetic factors inherited from parents.

It is regulated solely by feedback from peripheral organs.

It occurs independently of the hypothalamus.

It is influenced by hypothalamic hormones and physiologic demands. (correct)

What is the role of insulin-like growth factor I (IGF-I) in relation to growth hormone?

It mediates some growth hormone actions in peripheral tissues. Signup and view all the answers

What embryological origin does the posterior pituitary have?

Neuroectodermal origin from the hypothalamus Signup and view all the answers

What is the pars intermedia?

An avascular region between the anterior and posterior pituitary Signup and view all the answers

What term describes the relationship between the hypothalamus and the pituitary gland?

Hypothalamo-hypophyseal relationship Signup and view all the answers

How does the anterior pituitary receive signals for hormone secretion?

Via the bloodstream from the hypothalamus Signup and view all the answers

What percentage of chromophil cells in the anterior pituitary are somatotropes that secrete growth hormone?

30% to 40% Signup and view all the answers

Which of the following hormones is not classified as a glycoprotein secreted by the anterior pituitary?

Prolactin Signup and view all the answers

Which type of cell in the anterior pituitary is known to be non-secretory and serves as a precursor to chromophil cells?

Chromophobe cells Signup and view all the answers

The anterior pituitary is referred to as the master gland primarily because it regulates which of the following?

Other endocrine glands Signup and view all the answers

Which type of anterior pituitary cell is classified as basophilic and secretes adrenocorticotropic hormone (ACTH)?

Corticotropes Signup and view all the answers

What is the main difference between acidophil and basophil cells in the anterior pituitary?

Staining properties and secretory nature Signup and view all the answers

What peptide hormone is secreted by lactotropes in the anterior pituitary?

Prolactin Signup and view all the answers

Which of the following statements about the anterior pituitary gland is true?

Chromophobe cells make up about 50% of total cells. Signup and view all the answers

What is the primary function of the first 24 amino acids in adrenocorticotropic hormone (ACTH)?

Stimulates skin pigmentation Signup and view all the answers

Which hormone from the hypothalamus inhibits the release of growth hormone?

Growth hormone-inhibitory hormone Signup and view all the answers

Which hormone is primarily responsible for stimulating the anterior pituitary to release adrenocorticotropic hormone (ACTH)?

Corticotropin-releasing hormone Signup and view all the answers

Which of the following hormones secreted by the anterior pituitary is categorized as a tropic hormone?

Adrenocorticotropic hormone Signup and view all the answers

What is the role of releasing and inhibitory hormones secreted by the hypothalamus?

To regulate the secretion of hormones from the anterior pituitary Signup and view all the answers

Which two hormones are primarily stimulated by gonadotropin-releasing hormone (GnRH)?

FSH and LH Signup and view all the answers

What is the function of beta endorphin in the body?

Acts as a painkiller or neurotransmitter Signup and view all the answers

How are the releasing hormones from the hypothalamus transported to the anterior pituitary?

Through hypothalamo-hypophyseal portal vessels Signup and view all the answers

Study Notes

Pituitary Gland Objectives

After studying lectures 2&3, students should be able to describe the pituitary gland's structure and its relationship to function.
Define pituitary cell types, understand how their numbers are regulated by physiological demands, and describe the effects of growth hormone on growth and metabolism.
Define the role of Insulin-like Growth Factor I in mediating growth hormone actions.
List stimuli that regulate growth hormone secretion and explain the underlying mechanisms.
Understand abnormal pituitary function and growth hormone secretion, and how these conditions are treated.

Pituitary Gland Introduction

The pituitary gland, also called the hypophysis, is a small endocrine gland (1 cm in diameter, weighing 0.5-1 g).
It's located in the sella turcica of the sphenoid bone at the base of the skull.
It's connected to the hypothalamus by the pituitary stalk (hypophyseal stalk).
The pituitary gland is divided into two divisions: anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis).
These divisions, though close, arise from different embryonic origins (ectoderm vs. neuroectoderm).
They have distinct structures and functions.
A small, relatively avascular structure, called the pars intermedia, lies between the two divisions.

Pituitary Gland Anatomy and Development

Both anterior and posterior pituitary divisions develop embryologically from different sources.
The anterior pituitary arises from the pharyngeal epithelium (upward growth—Rathke's pouch).
The posterior pituitary originates from the hypothalamus as a downward diverticulum.
These two parts grow towards each other and fuse in the median region between the mouth cavity and brain.

Anterior Pituitary (Adenohypophysis) - Histology

The anterior pituitary has two major cell types: chromophobe cells and chromophil cells.
Chromophobe cells (50%): do not contain granules and stain poorly. They are thought to be precursor cells for chromophil cells.
Chromophil cells (50%): contain granules and stain darkly. These are further classified based on staining properties or secretory nature.

Anterior Pituitary Cell Types (Chromophil Cells)

Classification by staining:
Acidophilic (alpha cells, ~35%): stain acidophilically.
Basophilic (beta cells, ~15%): stain basophilically.
Classification by secretory nature:
Somatotropes: secrete growth hormone (GH).
Corticotropes: secrete adrenocorticotropic hormone (ACTH).
Thyrotropes: secrete thyroid-stimulating hormone (TSH).
Gonadotropes: secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
Lactotropes: secrete prolactin.

Regulation of Anterior Pituitary Secretion

The hypothalamus regulates anterior pituitary function by releasing and inhibiting hormones.
These hormones are transported to the anterior pituitary through hypothalamo-hypophyseal portal vessels.

Hypothalamic Releasing and Inhibiting Hormones

Specific hypothalamic hormones regulate the release of different anterior pituitary hormones.
Growth hormone-releasing hormone (GHRH) stimulates GH release.
Growth hormone-releasing polypeptide (GHRP) stimulates GHRH and GH release.
Growth hormone-inhibitory hormone (GHIH, or somatostatin) inhibits GH release.
Thyrotropin-releasing hormone (TRH) stimulates TSH release.
Corticotropin-releasing hormone (CRH) stimulates ACTH release.
Gonadotropin-releasing hormone (GnRH) stimulates FSH and LH release.
Prolactin-inhibitory hormone (PIH), primarily dopamine, inhibits prolactin release.

Anterior Pituitary Hormones (Tropic Hormones)

Some anterior pituitary hormones (e.g., ACTH, TSH, FSH, LH) are tropic hormones, meaning they stimulate other endocrine glands. Prolactin acts in a direct manner on target tissues (e.g., mammary glands).

Gonadotropic Hormones

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are collectively called gonadotropins as they affect the gonads.
LH and FSH are glycoproteins with specific subunit structures (alpha and beta). Their half-lives differ (e.g., LH ≈ 60 minutes).

Prolactin

Prolactin is a single-chain polypeptide (protein) hormone, with a specific molecular structure and a short half-life (e.g., about 20 minutes).
Prolactin is essential for mammary gland development and milk production/secretion in females.

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Description

This quiz covers lectures 2 and 3 about the pituitary gland, focusing on its structure, function, and role in growth hormone regulation. Students will explore pituitary cell types, their physiological regulation, and the effects of insulin-like growth factor I. Additionally, the quiz addresses abnormal functions and treatment of growth hormone-related conditions.