Endocrine system

1. Endocrine Glands

2. Learning Outcomes
1. Describe key features / morphological similarities of endocrine
organs
2. Enlist organs or entities with endocrine function in domestic animals
3. Describe the structure of major endocrine glands in domestic animals
along with basic functional correlates

3. Key features
Scattered component organs
Shared function – hormone synthesis
Linked functionally by circulatory system
Morphological similarities
sparse CT
extensive blood and lymphatic supply
epithelioid cell types
absence of secretory ducts

4. Primary endocrine glands
Pituitary
Thyroid
Parathyroid
Pineal
Adrenal
Both major endocrine and exocrine function
Testis (Anatomy and Histology courses, Semester II)
Ovary (Anatomy and Histology courses, Semester II)
Pancreas (Anatomy and Histology courses, Semester II)
Placenta (Embryology, Semester II)
Dispersed endocrine cells
Intraepithelial endocrine cells/Kidney/cardiac myocytes

5. THE HYPOPHYSIS
Ventral midline of diencephalon
Sella turcica
Stalk like connection to hypothalamus
– tuber cinereum
Hypothalamus-pituitary axis
Adenohypophysis
glandular parenchyma
extensive blood supply
reddish and friable
releases GH, FSH, LH, ACTH, TSH, Prolactin, MSH
Neurohypophysis
pale and fibrous
stores and releases Oxytocin & ADH
Vascularization
Internal carotid artery

7. THYROID GLAND
Dark red paired structure – lobes
Ventrally placed connecting isthmus -
glandular
Extends from cricoid cartilage to 5th
tracheal ring
Vascularization
Cranial + caudal thyroid arteries

8. Dog Goat Ox Horse

10. PARATHYROID GLANDS
2 pairs of small ellipsoid discs
cranial dorsolateral edge of thyroid – external pair
embedded in caudal thyroid – internal pair
Vascularization
Common with thyroid glands

11. PINEAL GLAND
Part of the diencephalon - epithalamus
Unpaired – on the dorsal midline of diencephalon
Variable size
Secretes melatonin, serotonin
important in seasonality of reproductive cycles
"biological clock“
Vascularization
Pial circulation

12. ADRENAL GLAND
Paired
Craniomedial to the corresponding kidney
NO functional relationship with the kidneys
Outer cortex
Inner medulla
Vascularization
Abdominal aorta
Phrenicoabdominal
Lumbar aa
Renal aa

13. Testis
Interstitial cells of Leydig (Androgens)
Sustenticular cells (Activin, Inhibin)
Ovary
Granulosa cells (Estrogen) / corpus luteum (Progesterone)
Pancreas
Islets of Langerhans (Insulin, glucagon, somatostatin, pancreatic polypeptide)
Placenta
Equine chorionic gonadotropin, Progesterone, Lactogen, Relaxin
ORGANS WITH BOTH MAJOR ENDOCRINE & EXOCRINE
ROLES

14. DISPERSED ENDOCRINE CELLS
Enteroendocrine cells
Pyloric glands/ duodenal
Endocrine cells of Kidney
Juxtaglomerular cells (Renin)
APUD
Amine precursor uptake and decarboxylation

15. Reference
Chapter 6; Textbook of Veterinary Anatomy, 4th Ed
Dyce, Sack, Wensing
Chapter 15; Veterinary Anatomy of Domestic Mammals, 6th Ed
Koenig & Liebich