20-21 The Endocrine System
I. Overview
II. Pituitary
III. Adrenals
IV. Pancreas
V. Thyroid
VI. Parathyroids
General structure: fenestrated capillaries
http://www.ama-assn.org/ama/pub/category/7157.html
I. Pituitary
A. Development
1. neurohypophysis (post. Lobe) (20.1)
a. develops as outgrowth of diencephalon
b. forms:
1) pars nervosa (posterior lobe – note error in 20.1)
2) infundibulum
I. Pituitary
A. Development
2. adenohypophysis ( ant. Lobe) (20.1)
a. develops from Rathke’s pouch
1) oral ectoderm
b. forms:
1) pars distalis (anterior lobe)
2) (pars tuberalis & pars intermedia)
I. Pituitary
B. Hypothalamo-hypophyseal portal system (20.2)
1. primary capillary plexus
a. base of infundibulum / hypothalamus
2. veins to anterior lobe
3. secondary capillary plexus
4. transports neurohormones
a. releasing hormones
b. inhibiting hormones
I. Pituitary
C. Pars distalis 20.6
1. Chromophobes & chromophils
2. basophils
a. gonadotrophic cells
1) FSH
2) LH
b. thyrotropic cells
1) TSH
c. corticotrophic cells
1) ACTH
I. Pituitary
C. Pars distalis
3. acidophils
a. somatotropic cells
1) GH
b. mammotropic cells
1) PRL
I. Pituitary
D. Neurohypophysis (20.3)
1. pituicytes
2. neurosecretory cells
3. ~100,000 unmyelinated axons from hypothalamus
I. Pituitary
D. Neurohypophysis 20-9
I. Pituitary
D. Neurohypophysis 20.7
4. vasopressin / ADH
a. contraction of smooth muscle in arteries
b. increase reabsorption of H2O in collecting tubules
5. oxytocin
a. contraction in pregnant uterus
III. Adrenals
A. Overview (21.2)
1. adrenal cortex
a. steroids
2. adrenal medulla
a. E & NE
3. stroma
a. capsule
b. trabeculae
c. reticular fibers
4. extensive capillary plexuses
III. Adrenals
B. Adrenal cortex (21.2)
1. zona glomerulosa (21.3)
a. 15% of adrenal cortex
III. Adrenals
B. Adrenal cortex
1. zona glomerulosa
b. clusters of cells (21.3)
c. mineralocorticoids (aldosterone)
1) increase DCT absorption of Na+
III. Adrenals
B. Adrenal cortex
2. zona fasciculata (21.3)
a. 65% of adrenal cortex
b. cells in cords (21.3)
III. Adrenals
B. Adrenal cortex
2. zona fasciculata
c. many lipid droplets in cytoplasm (21.3)
d. glucocorticoids (cortisol & corticosterone)
1) influence CHO metabolism
2) suppress immune response
III. Adrenals
B. Adrenal cortex
3. zona reticularis (21.3)
a. 7% of adrenal cortex
III. Adrenals
B. Adrenal cortex
3. zona reticularis
b. irregular cords in network (21.5)
c. lipofuscin granules
d. androgens
e. little effect vs. testicular hormones
III. Adrenals
C. Adrenal medulla (21.3)
1. cells in cords
2. secrete E & NE
3. innervated by preganglionic sympathetic (myelinated) axons
III. Adrenals
Adrenal medulla
Look for:
IV. Pancreas (Islets of Langerhans)
http://diabetes.niddk.nih.gov/dm/pubs/dictionary/P-T.htm
IV. Pancreas (Islets of Langerhans)
A. Cluster of cells in cords (21.9)
1. network of fenestrated capillaries
IV. Pancreas (Islets of Langerhans)
A. Cluster of cells in cords
2. A cells: glucagon, incr. blood sugar (21.11)
[immunohistochemistry for glucagon cells]
IV. Pancreas (Islets of Langerhans)
A. Cluster of cells in cords
3. B cells: insulin, decr. blood sugar (21.12)
4. D cells: somatostatin: inhibits A & B cells
5. E cells: unknown function
[immunohistochemistry for insulin]
V. Thyroid
A. Gross Anatomy (21.15)
1. anterior to larynx
2. two lobes connected by isthmus
3. well vascularized
V. Thyroid
B. Follicles (21.16,21.17)
1. squamous to columnar epithelium
a. squamous = inactive
b. columnar = active
2. colloid
a. thyroxine / T4
b. triiodothyronine / T3
3. stimulates rate of metabolism
4. Influenced by TSH
V. Thyroid
C. Parafollicular cells (21.18)
1. calcitonin
a. decr. blood Ca++
VI. Parathyroid glands
A. Gross anatomy (21.22)
1. four small glands
2. located on posterior of thyroid gland
VI. Parathyroid glands
Microscopic anatomy 21.16
VI. Parathyroid glands
B. Parenchyma
1. oxyphil cells (21.24)
a. larger, polygonal cells
b. unknown function
VI. Parathyroid glands
2. chief cells 21.23
a. pale, acidophilic cytoplasm� b. secretes parathyroid hormone� c. incr. blood Ca++ levels�