Pg 135 1 Thyroid Gland The thyroid gland

Thyroid Gland • The thyroid gland has two lateral lobes and lies on either

Structure of the Gland Larynx Thyroid gland Colloid Follicular cells Colloid Isthmus (a) Extrafoll

Thyroid Hormones OH I I O I CH 2 I I CH 2 NH

Parathyroid Glands • The parathyroid glands are on the posterior surface of the thyroid

Structure of the Glands Pharynx Secretory cells Thyroid gland Capillaries Parathyroid glands © R.

Parathyroid Hormone Foods Cholesterol Intestinal enzymes Provitamin D Ultraviolet light in skin Vitamin D

Parathyroid glands (on posterior of thyroid gland) Release into bloodstream Decreased blood calcium stimulates

Slides: 11

Download presentation

Pg. 135 1

Thyroid Gland • The thyroid gland has two lateral lobes and lies on either side of the larynx, over the trachea • About 2 inches long, with lobes joined by strands of thyroid tissues called the isthmus • Rich blood supply • It secretes three hormones: • T 4 (thyroxine) • T 3 (triiodothyronine) *5 to 10 x more active than thyroxine* • BOTH control rate of metabolism, stimulate protein synthesis, stimulates breakdown of liver glycogen to glucose • Calcitonin-controls calcium level in bloodstream 2

Structure of the Gland Larynx Thyroid gland Colloid Follicular cells Colloid Isthmus (a) Extrafoll icular cell Extrafollicular cells © Fred Hossler/Visuals Unlimited 3

Thyroid Hormones OH I I O I CH 2 I I CH 2 NH 2 CHCOOH Thyroxine (T 4) Triiodothyronine (T 3) 4

Parathyroid Glands • The parathyroid glands are on the posterior surface of the thyroid gland • There are typically four tiny parathyroid glands the size of grains of rice • It secretes one hormone: -PTH (parathyroid hormone or parathormone)-also controls concentration of calcium in bloodstream; stimulates increase in number and size of osteoclasts 6

Structure of the Glands Pharynx Secretory cells Thyroid gland Capillaries Parathyroid glands © R. Calentine/Visuals Unlimited Esophagus Trachea Posterior view 7

Parathyroid Hormone Foods Cholesterol Intestinal enzymes Provitamin D Ultraviolet light in skin Vitamin D (Cholecalciferol) Also obtained directly from foods Liver Hydroxycholecalciferol Kidney Stimulated by PTH Dihydroxycholecalciferol (active form of vitamin D) Controls absorption of calcium in intestine Ca+2 8 Ca+2

Parathyroid glands (on posterior of thyroid gland) Release into bloodstream Decreased blood calcium stimulates parathyroid hormone secretion Stimulation – Increased blood calcium inhibits PTH secretion Inhibition PTH Bloodstream PTH Ca+2 + Bone releases Ca+2 PTH + Ca+2 Kidneys conserve Ca+2 and activate Vitamin D Ca+2 Intestine absorbs Ca+2 Active Vitamin D 9