Anatomy of Pituitary Gland

Question 1

The pituitary gland is also known as?

Answer 1

hypophysis

Question 2

Where is this pituitary gland?

Answer 2

lies immediately beneath the hypothalamus

Question 3

Describe the 2 functional components?

Answer 3

1. anterior lobe (adenohypophysis) - glandular epithelial tissue 2. posterior lobe (neurohypophysis) - neurosecretory tissue

Question 4

The anterior lobe is derived from?

Answer 4

from the evagination of the ectoderm of the roof of the mouth (oropharynyx) - this protrusion is called Rathke’s pouch

Question 5

The posterior lobe is derived from?

Answer 5

from a downgrowth of the (future infundibulum) of neuroectoderm of the floor of the third ventricle (the diencephalon of the developing brain)

Question 6

Describe the subdivisions of the adenohypophysis?

Answer 6

1. pars distalis - the largest section 2. pars tuberalis - a collar of tissue that usually surrounds the infundibular stalk 3. pars intermedia - a narrow band that is usually separated from the pars distalis by a hypophyseal cleft

Question 7

Describe the subdivisions of the neurohypophysis?

Answer 7

1. Pars nervosa - the bulk of the posterior pituitary 2. Median emminence - the upper section of the neurohypophysis above the pars tuberalis 3. Infundibular stalk - the “stem” that connects the pars nervosa to the base of the brain

Question 8

The pars distalis is composed of?

Answer 8

1. winding cords of epithelial cells 2. vascular sinusoids

Question 9

What are the cell types in the pars distalis?

Answer 9

1. Acidophils - have cytoplasm that stains red or orange 2. Basophils - have cytoplasm that stains a bluish color 3. Chromophobes - have cytoplasm that stains very poorly

Question 10

State 3 methods to define different cell types of pars distalis?

Answer 10

1. histochemistry - PAS – reacts with carbohydrates of glycoproteins 2. histophysiological studies - staining + physiological manipulation of the target organ 3. EM and immunocytochemistry - use of antibodies

Question 11

What kind of cells are acidophils?

Answer 11

cells that produce polypeptide hormones

Question 12

What kind of cells are basophils?

Answer 12

cells that produce glycoprotein hormones

Question 13

Describe the cells known as acidophils?

Answer 13

1. somatotropes - produce growth hormone 2. lactotropes - produce prolactin

Question 14

Describe the cells known as basophils?

Answer 14

1. thyrotropes - produce thyroid stimulating hormone 2. gonadotropes - produce luteinizing hormone/follicle-stimulating hormone 3. corticotropes - produce adrenocorticotrophic hormone

Question 15

Why can acidophils also stain bright purple with PAS stains?

Answer 15

due to the high carbohydrate content of the hormones within acidophils

Question 16

Describe the cells known as chromaphobes?

Answer 16

1. have minimal or no hormonal content 2. may be acidophils or basophils that have degranulated and thereby are depleted of hormone 3. may also represent stem cells that have not yet differentiated into hormone-producing cells

Question 17

The pars tuberalis is composed of?

Answer 17

1. cords of epithelial cells 2. hypophseal portal vessels

Question 18

Name the cells in the pars tuberalis?

Answer 18

1. gonadotropes 2. thyrotropes 3. other secretory cells of unknown function

Question 19

Describe the pars intermedia?

Answer 19

is closely associated with pars nervosa and separated from the pars distalis by the hypophyseal cleft

Question 20

Describe the cells of the pars intermedia?

Answer 20

contains large pale cells that often surround follicles filled with ill-defined “colloid”.

Question 21

Name the hormone predominently secreted by pars intermedia?

Answer 21

melanocyte-stimulating hormone

Question 22

State the 3 areas of the neurohypophysis?

Answer 22

1. median eminence 2. infundibular stalk 3. infundibular process - the bulk of the neurohypophysis

Question 23

Name the 3 cell types of the pars nervosa?

Answer 23

1. largely unmyelinated axons from hypothalamic neurosecretory neurons 2. glial cells 3. pituicytes - poorly defined cells

Question 24

Describe the neurons in the pars nervosa?

Answer 24

axons have their cell bodies in the paraventricular and supraoptic nuclei of the hypothalamus - so only axons are part of the pars nervosa

Question 25

What hormones do these neurons secrete?

Answer 25

oxytocin or antidiuretic hormone

Question 26

Describe a histologic feature of the neurohypophysis?

Answer 26

herring bodies - dilated areas or bulges in the terminal portion of axons that contain clusters of neurosecretory granules : often are seen in association with capillaries

Question 27

What do the granules of Herring bodies contain?

Answer 27

1. oxytocin or antidiuretic hormone 3. neurophysins

Question 28

Describe the blood supply to the pituitary gland?

Answer 28

Superior hypophyseal artery from Int. Carotid aa. ramifies into a capillary bed in the lower hypothalamus

Question 29

Describe the venous drainage of the pituitary gland?

Answer 29

1. Blood from those capillaries drains into hypothalamic - hypophyseal portal veins 2. Capillaries within the anterior pituitary, coalesce into veins that drain into the systemic venous blood 3. Those veins also collect capillary blood from the posterior pituitary gland.

Question 30

What is the pineal gland?

Answer 30

1. The pineal body is a flattened, cone-shaped organ attached to the roof of the third ventricle, where it occupies a depression between the superior colliculi 2. The pineal body is surrounded by pia mater, which subdivide it into lobules

Question 31

Describe the 2 cell types in the pineal gland?

Answer 31

1. pinealocytes - about 95% of the cells; large, light and round nuclei 2. astrocytes - glial cells; dark, elongated nuclei : In addition it contains calcified concretions called corpora arenacea or brain sand

Question 32

State the functions of the pineal gland?

Answer 32

1. Relates light intensity and duration of endocrine activity 2. Photosensitive organ 3. Produces melatonin - During daytime, Melatonin poduction is inhibited by light --- increases GnRH----FSH & LH 3. Produces neurotransmitters

Question 33

How is the pineal gland a photosensitive organ?

Answer 33

regulator of day/night cycle (circadian rhythm) --- retinohypothalamic tract ----- pineal gland

Question 34

Give examples of the neurotransmitters produced by the pineal gland?

Answer 34

1. serotonin 2. norepinephrine 3. dopamine 4. histamine 5. somatostin

Question 35

What is a pinealoma?

Answer 35

tumour of the pineal gland

Question 36

What is a pinealoma associated with?

Answer 36

precocious puberty - 1. Onset of androgen secretion at 9-10 yrs in boys 2. Onset of estrogen secretion at 8 years in girls

Question 37

State a consequence of a pinealoma?

Answer 37

can cause Parinaud’s syndrome (neurological disorder ) - paralysis of upward gaze