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Chapter 5

BIOD27H3 Chapter Notes - Chapter 5: Gonadotropin, Luteinizing Hormone, Thyroid-Stimulating Hormone

Biological Sciences
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Chapter 5 pituitary Hormones
-Female Pit gland is much smaller than Males
-Females becomes larger during pregnancy
Anatomy of the Pituitary Gland
- Also known as hypophysis
- Composed of tissues derived from two diverse origins. Embryological origins of adenohypophysis and
neurohypophysis are different
- Composed of : adenohypophysis (anterior lobe) and neurohypophysis( posterior lobe)
- mostly glandular tissue
-composed of pars distalis and tuberalis
- consists of neuronal processes that originate from neurons in the hypothalamus
-composed of pars Nervosa
Vascularisation and Innervation
Size of each lobe of the pit gland varies between diff species and may reflect the hormonal output of the
glands required for successful adaptation to a particular habitat
The pituitary gland receives its blood supply from the superior and inferior hypophysial arteries
Superior and Inferior branches of Superior hypophyseal artery penetrates the stalk and the hypothalamus
Pars distalis
- is vacularized by hypophyseal portalvessels that arise from capillary bed from the hypothalamus
- No evidence that neurons innervate or otherwise influence cell activity of pars distalis
Pars Nervosa
- receives a separate blood supply from the inferior hypophysial artery
- composed of axonal endings of neurons whose cell bodies are located in hypothalamic nuclei
- hypothalamic nuclei: paraventricular nuclei and supraoptic nuclei
- all hormones produced by the post. Lobe are released directly in to the efefretn portal veins to be
carried through the systematic circulation to act at target tissues
- some evidence indicates that some adenohypophyseal blood maybe shunted to the
neurohypophysis pit hormones may be able to modify CNS function
Cytotogical Methods Distinguish Different Pituitary Cell Types
Pars distalis
- cells are differentiated into somatotrophs, lactotrophs (mamotrophs), corticotrophs, thytotrophs, and
- ^ terms relate to hormonal product synthesized by each of these cells
- The cell types can slo be referred to as acidophils, basophils and chromophobes depending on their
affinity for certain dyes
- Acidophils: somatotrophs and lactotrophs
- Basophils: thyrotrophs and corticotrophs
- Chromophobes: corticotrophs. Corticotrophs are basophils but are usually classified as chromophobes
- The extent to which these cells exhibit acidophila, basophilia etc depends on the granular content of
the cell(hormonal vesicles) which varies with the temporal secretory activity of the cell
Nongranulated cell types are also present in both ant. And post. Lobes
i.e glia cells
the processes of glial cells often separate one pituitary cell from contact with another
although each of the pituitary hormones is localized to a particular cell type, exception is gonadotrophs
gonadotrophs contain both of the gonadotrophic hormones : lutropin and fullotropin
subpopulations of gonadotrophs contain only one of the gonadotropins.
Hormones of the pituitary
Number of peptide hormones are produced by ht epituitary
These hormones regulate such target organs: adrenals, thyroid gland, gonads
The mammary glands, uterus, kidneys and other tissues are also controlled by the hypophyseal hormones
2 gonadotrophis : follicle-stimulating hormone (FSG) or follitropin and luteinizing hormones (LH)
TSH: thyroid-stimualtign hormone or thyrotropin
- Regulates thyroid activity
ACTH : adrenal cortical-stimulating hormone or adrenocorticotropin
- Regulates adrenal activity
Growth Hormone: has generalized growth-promoting effects
PRL; prolactin: has more specific growth-promoting action on the mammary glands
MSH: melanocyte-stimualting hormone is produced by cells of pars intermedia
Neurohypophysial hormones: oxytocin and vasopressin , both formed within neurons of the
neurohypophysis whose cellbodies originate within the hypothalamus
The pit hormones are released into the bloodstream where they circulate to interact with their cells of
target organs
Pituitary Hormones can be grouped in to Families of Structurally Related Proteins
The hormones of the pituitary can be classified in to 4 groups based on their structural similarity and
presumed evol. Origin:
1) GH and prolactin produce numerous similar sequences of amino acids within their individual
structures and they are las