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Endocrine: Pituitary I
Terms in this set (93)
What secretions does the endocrine system produce?
Hormones (chemical messengers)
Hormones help maintain...
Do endocrine glands use ducts?
NO - they are ductless
How are hormones transported?
Via connective tissue spaces and the vascular system
What are the 3 Hormone Types?
1. Steroid Hormones
2. Small peptides, proteins, and glycoproteins
3. Amino acid analogues and derivatives including catecholamines (norepinephrine and epinephrine)
How are steroid hormones synthesized?
Synthesized and secreted by cells of the ovaries, testes, and adrenal cortex
Steroid hormones are derived from what?
How are small peptides, proteins, and glycoproteins synthesized?
Synthesized and secreted by cells of the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, pancreas, and enteroendocrine cells
How are amino acid derivatives synthesized?
Synthesized and secreted by neurons and cells of the adrenal medulla
Thyroid hormones are also considered...
... the iodinated amino acids
What do hormones interact with?
Specific hormone receptors
What do hormones do?
They alter biologic activity of target cells
What are the two receptor types?
1. Cell Surface Receptors
2. Intracellular Receptors
What do cell surface receptors interact with?
Peptide hormones or catecholamines
Are hormones that use cell surface receptors able to pass through the cell membrane?
What happens when cell surface receptors are activated?
It generates large amounts of intracellular molecules called second messengers
What is the function of second messengers?
They amplify the signal initiated by the hormone-receptor interaction
What produces second messengers?
The activation of membrane associated G proteins
Adenylate Cyclase/ cAMP system is used for...
... most protein hormones and catecholamines
Tyrosine Kinase system is used for...
... Insulin and epidermal growth factor
Phosphatidyl inositol system is used for...
... Certain hormones like oxytocin, gonadotropin-releasing hormone, angiotensin II and neurotransmitters such as epinephrine
Guanylate cyclase/ cGMP system is used for...
... An antagonistic system for the action of cAMP in some protein hormones
The majority of second messengers have what function?
They alter the cell's metabolism and produce hormone specific responses
What molecule is mainly responsible for an inhibitory response?
cGMP which interfere with the production of cAMP
Where are intracellular receptors localized?
Mainly within the cell, in the nucleus
What type of hormones use intracellular receptors?
Steroid hormones and thyroid hormones
Can the hormones that use intracellular receptors pass through the cell membrane?
What are the 3 binding domains of intracellular receptors?
1. Hormone binding region
2. DNA binding region
3. Amino-terminal region
What do steroid and thyroid hormones influence?
They directly influence gene expression
Are second messengers required for steroid and thyroid hormones?
What happens when a steroid or thyroid hormone binds to intracellular receptors?
It causes an allosteric transformation of the receptor into a form that binds to chromosomal DNA and activates RNA polymerase
- increase of mRNA
- production of new proteins that regulate cell metabolism
What is the gastroenterohepatic system (GEP)?
The largest collection of endocrine cells in the body
What is the function of GEP cells?
They exercise autocrine and paracrine control of their own activity and adjacent epithelial cells
What is the pituitary gland attached to?
Describe the relationship between the pituitary gland and the hypothalamus.
They are morphologically and functionally linked in the endocrine and neuroendocrine control of other endocrine glands
What are the "master organs" of the endocrine system?
The pituitary gland and the hypothalamus
What gland is larger in mulitparous women?
The pituitary gland
Where is the pituitary gland located?
Within the sella turcica of the sphenoid bone
What covers the pituitary gland?
A flap of dura mater called the diaphragm sellae
How is the pituitary gland connected to the hypothalamus?
Via the infundibulum and a vascular network
What are the two functional components of the pituitary gland?
- Anterior lobe (adenohypophysis)
- Posterior lobe (neurohypophysis)
What type of tissue makes up the anterior lobe of the pituitary gland?
Glandular epithelial tissue
From what does the anterior lobe of the pituitary develop?
It develops as an evagination from the oropharynx ectoderm - known as Rathke's Pouch
What are the derivatives of Rathke's Pouch?
1. Pars distalis
2. Pars intermedia
3. Pars tuberalis
Pars distalis arises from...
...the anterior wall of the pouch
Pars intermedia arises from...
... the posterior wall of the pouch
Pars tuberalis arises from...
...the lateral walls of the pouch
What does pars tuberalis form?
A collar or sheath around the infundibulum
Which derivative comprises the bulk of the anterior lobe of the pituitary?
What type of tissue makes up the posterior lobe of the pituitary gland?
Neural secretory tissue
From where is the posterior lobe of the pituitary gland derived?
From the diencephalon
What are the two parts of the posterior lobe of the pituitary gland?
1. Pars nervosa
What does pars nervosa contain?
Neurosecretory axons and their endings
What does the infundibulum contain?
Neurosecretory axons that form the hypothalamohypophyseal tracts
The blood supply of the pituitary gland comes from what two vessels?
1. Superior hypophyseal arteries
2. Inferior hypophyseal arteries
What do the superior hypophyseal arteries supply?
Pars tuberalis, median eminence, and infundibulum
What do the inferior hypophyseal arteries supply?
Primarily the pars nervosa
What gives rise to the fenestrated capillaries of the hypothalamohypophyseal portal system?
The superior hypophyseal arteries
Where do the fenestrated capillaries of the hypothalamohypophyseal portal system drain?
Into the hypophyseal portal veins
What do the hypophyseal portal veins give rise to?
A second fenestrated sinusoidal capillary network
What is the function of the hypothalamohypophyseal portal system?
It carries the neuroendocrine secretions of the hypothalamic nerves from sites of release in the median eminence and infundibulum directly to the cells of pars distalis
Where does most of the blood from the pituitary gland drain?
It drains into the cavernous sinus
What does the anterior lobe of the pituitary gland secrete?
Hormones that regulate other endocrine glands and some non-endocrine tissues
How are cells arranged in the anterior lobe of the pituitary gland?
In clumps and cords separated by fenestrated sinusoidal capillaries
What are the hormones of the anterior lobe of the pituitary gland?
1. Growth hormone (GH)
2. Prolactin (PRL)
3. Adrenocorticotropic hormone (ACTH)
4. Follicle Stimulating hormone (FSH)
5. Luteinizing hormone (LH)
6. Thyroid Stimulating hormone (TSH)
What is the function of growth hormone?
Growth of the body
What is the function of prolactin?
Mammary gland development, milk formation
What is the function of adrenocorticotrophic hormone?
Maintains structure and stimulates hormone secretion from the adrenal cortex
What is the function of follicle stimulating hormone?
Follicular development in the ovary, spermatogenesis in testes
What is the function of luteinizing hormone?
Stimulates formation of the corpus luteum, stimulates interstitial cells of Leydig in testes to secrete testosterone
What is the function of thyroid stimulating hormone?
Stimulates growth of the thyroid gland and the release of thyroid hormones
What four hormones of the anterior lobe of the pituitary gland are considered tropic?
What are tropic hormones?
They regulate the activity of cells in other endocrine glands
What are non tropic hormones?
They act directly on target organs that are not endocrine glands
What hormones are considered non tropic?
How are the cells arranged in pars distalis?
They are arranged in cords or nests with interweaving capillaries
How are cells of pars distalis identified?
Histochemistry, histophysiologic studies, electron microscopy, and immunocytochemistry
All known hormones of the anterior pituitary are...
...small proteins or glycoproteins
What are the 5 cell types of pars distalis?
- produce somatotropin or growth hormone
- Produce prolactin and increase in size during pregnancy
- Product proopiomelanocortin (POMC)
When POMC is cleaved, what does it fragment into?
- Beta-Lipotrophic hormone
- Melanocyte Stimulating Hormone (MSH)
FSH, LH Cells
- many are capable of producing both FSH and LH which play an important role in male and female reproduction
- Produce thyrotropic hormone
What does pars intermedia surround?
A series of small cystic cavities that represent the remnants of Rathke's Pouch
What is pars tuberalis?
An extension of the anterior lobe along the infundibulum
What is the cause of gigantism and acromegaly?
Excessive secretion of growth hormone due to the presence of adenoma
...if the growth hormone secreting tumor occurs during childhood and puberty when the epiphyseal plates are still active
...if excessive growth hormone secretion occurs in the adult when the epiphyseal plates are inactive
What leads to gonadotropin deficiency?
Prolactin secreting tumors that alter the hypothalamic-hypophyseal-gonadal interaction
What is hypersecretion in women linked to?
Infertility caused by the lack of ovulation and oligomenorhea or amenorhea
What is galactorrhea?
- common problem in hyperprolactinemia
THIS SET IS OFTEN IN FOLDERS WITH...
Endocrine: Pituitary II
Endocrine: Thyroid and Parathyroid Glands
Endocrine: Adrenal Glands
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