Endocrine

Question 1

What is the endocrine system composed of/ what’s its function?

Answer 1

Composed mainly of ductless glands that secrete hormones directly into the bloodstream.

Functions as long-range communication network that regulates homeostasis, works in conjunction with the nervous system.

Question 2

What are the 3 components of the endocrine system?

Answer 2

Separate glands of purely endocrine function. Includes pituitary (hypophysis), thyroid, parathyroid, adrenals.

Scattered masses of endocrine tissue within exocrine glands or other organs. Includes pancreas, Leydig’s cells (testis), corpora lutea (ovary), juxtaglomerular apparatus in kidney.

Isolated endocrine cells - principally cells within the epithelial lining of digestive and respiratory tracts.

Question 3

Leydig cell secretion

Answer 3

testosterone

Question 4

corpora lutea secretion

Answer 4

progesterone

Question 5

juxtaglomerular apparatus secretion

Answer 5

rennin

Question 6

Hormonal communication of the endocrine system requires what?

Answer 6

Endocrine tissue is highly vascularized to facilitate transport of hormones

1. Receptors in target cell which recognize hormone and bind to it.
2. Mechanism for translating binding of hormone to response (e.g., Second Messengers in the case of peptide hormones).

Question 7

Describe the pituitary gland generally.

Answer 7

Exists as an endocrine “extension” of hypothalamus (the part of the brain that mediates visceral functions of the body), enclosed in a dense fibrous CT capsule.

Question 8

Name the 2 major parts of the pituitary gland.

Answer 8

Adenohypophysis = Anterior Pituitary; originates as an invagination from the roof of the mouth (Rathke’s Pouch).

Neurohypophysis = Posterior Pituitary; originates as an evagination from the floor of the diencephalon region of the brain (Infundibulum)

Question 9

What can be said about the pituitary gland of all vertebrates?

Answer 9

present in all vertebrates

origin is the same, organization is different

Question 10

Adenohypophysis

Answer 10

Vascular capillaries among cords and clumps of glandular epithelium.

(glandular epithelium component) includes:

Pars distalis
Pars tuberalis
Pars intermedia

Question 11

Pars distalis

Answer 11

Consists of glandular epithelial cells in cords and clusters surrounding fenestrated capillaries, forms bulk of pituitary (75%), supported by a delicate reticular CT stroma.

Question 12

Cell types of the pars distalis

Answer 12

1. Acidophils = stain acidophilic; secrete GH and Prolactin; compact dark nuclei, cell outlines distinct.
2. Basophils = stain basophilic; secrete TSH, FSH, LH, and ACTH; fewer but larger nuclei, not as dark staining
3. Chromophobes = pale-staining cells, relatively little cytoplasm; appear to be chromophils in degranulated, quiescent state; basophilic nuclei; Most abundant cell type

Question 13

Pars tuberalis

Answer 13

forms collar of cells around infundibular stalk; cells arranged in groups or short cords - include acidophils, basophils, undifferentiated chromophobes; secretes gonadotropins mainly.

Question 14

pars intermedia

Answer 14

poorly developed (in humans) layer of basophil and chromophobe cells lying between pars distalis and neurohypophysis.

In adult, remnants of lumen of Rathke’s Pouch (= hypophyseal cleft) fills with colloid and appears as a cyst.

Produces Melanocyte Stimulating Hormone (MSH) in amphibians and fish. (changes skin color to environment)

Question 15

Components of the neurohypophysis

Answer 15

pars nervosa
infundibular stalk

both are histologically identical. Contain axons from neurosecretory cells in hypothalamus and glial cells (pituicytes)

Question 16

Neurohypophysis facts

Answer 16

Pars nervosa serves as center for storage and release of oxytocin and vasopressin (ADH).

These are called posterior pituitary hormones since they are released from axon terminals in pars nervosa (although they are produced in nuclei of hypothalamus).

Herring Bodies = accumulations of secretory material, stain basophilic

Question 17

Describe the hypothalamo-anterior pituitary connection.

Answer 17

Intimate vascular “connection” occurs between hypothalamus/median eminence of infundibular stalk and adenohypophysis.

Communication by diffusion of hypothalamic hormones from capillaries in infundibular stalk to cells of adenohypophysis.

Diffusion of hypothalamic hormones into glandular epithelium (from portal vessels) directs cells of the adenohypophysis to produce hormones or inhibit production of hormones.