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Flashcards in HARC ENDOCRINE Deck (12):
1

The pituitary gland

• Attaches to the hypothalamus via the infundibulum
• Anterior pituitary consists of pars distalis and pars tuberalis
• Posterior pituitary - Pars nervosa and pars intermedia

2

Hypothalmus and anterior pituitary relationship

1. Superior hypophyseal artery enters the hypothalamus.
2. SUPERIOR HYPOPHYSEAL ARTERY forms the primary plexus of the hypophyseal portal system
3. Obove the optic chiasm, within the hypothalamus are neurosecretory cells which synthesise hypothalamus hormones and release them into the primary plexus
4. PRIMARY PLEXUS forms HYPOPHYSEAL PORTAL VEINS THEN into SECONDARY PLEXUS VEINS in the pituitary gland
5. Hypothalamus hormones act on anterior pituitary cells to stimulate release of hormone
6. Pituitary hormones pass out via ANTERIOR HYPOPHYSEAL VEIN into the general circulation to target organ

3

Human growth hormone (MECHANISM)

1. Growth hormone releasing hormone by hypothalamus (somatocrinin)
2. Somatotrophs in Anterior pituitary release HgH
3. Hgh stimulate tissue to release IGF
4.IGF increases glycolysis
5. hyperglycaemia stimulate hypothalamus to release Growth hormone inhibiting hormone (somatostatin)

4

Thyroid stimulating hormone (thyrotropin) (MECHANISM)

1. Hypothalamus releases thryotropin releasing homone (TRH)
2. Thyrotrophs in AP release thyroid stimulating hormone (TSH)
3. Stimulates thyroid hormone release
4. Inhibited by somatostatin

5

Lutenizing hormone (LH) (MECHANISM)

1. hypothalamus release gonadotropin releasing hormone
2. Stimulate gonadotroph to release FSH and LH

6

Prolactin (MECHANISM)

1. Prolactin releasing hormone / Prolactin inhibiting hormone can also be released from hypothalamus
2. Lactotrophs release Prolactin

7

ACTH (MECHANISM)

1. Corticotropin releasing hormone from hypothalamus
2. Corticotrophs release ACTH

8

Melanocyte stimulating hormone ( MSH) (MECHANISM)

1. Corticotropin releasing hormone from hypothalamus
2. Corticotrophs release MLH
3. Inhibited by dopamine

9

Functions of Insulin like growth factors

1. Cause cells to grow and increase amino acid uptake into cells
-> accelerate protein synthesis
-> increase muscle and bone growth

2. Enhance liplysis in adipose tissue
-> inc fatty acid for atp produc

3. Decrease glucose uptake and increase blood glucose levels

10

Function of posterior pituitary

• Axon terminals of neurosecretory cells
• Cell bodies of neurosec cells are in
- paraventricular nuclei
-supraoptic nuclei of hypothamus
• no synthesis of hormones
• Stores and releases two hormone
- oxytocin
- antidiuretic hormone

11

Blood supply to posterior pituitary

1. Inferior hypophyseal arteries
2. drain into capillary plexus of infundibular process - network recieves secreted oxytocin and antidiuretic hormone
3. Posterior hypophyseal vein - distribution to target cells in other tissues

12

Oxytocin

1. During delivery, stretching of the cervix of the uterus stimulates release of oxytocin
• Enhances contraction of smooth muscles cells in the wall of uterus

2. After delivery, it stimulates milk ejection from mammary glands in response to mechanical stimulus by suckling infant