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Anatomy 113 Endocrine Glands
Endocrine Glands |
Ductless Glands that secrete their hormones into the blood stream directly. |
Endocrine System |
The endocrine system, works along the nervous system, in the regulation and integrationof body processes. It plays a significant role in the maintainence of a controlled environment in which the cells of the body can optimally carry out their activities. |
Name the major endocrine glands |
1. Pineal Glands
2.Pituitary Gland
3.Thyroid Gland
4.Parathyroid Gland
5.Thymus
6.Adrenal Gland
7.Pancreas
8.Gonads - ovary and testes
9.Special secretory cells of the GI tract |
Characteristics of endocrine galnds |
1.Secretion of hormones
2.Ductless glands
3.Very Vascular
4.Target tissue
5.Slow but long lasting |
1.Secretion of hormones |
Chemical messengers or regulators that affect the activity of other cells. |
2.Ductless glands |
Do not have ducts to carry the secreted hormones so, ductless. Secrete the hormones directly into the blood stream. |
3.Very Vascular |
Have rich blood supply. |
4.Target tissue |
Affect activity of apecific target tissues. |
5.General effect |
Slow but effect is long lasting. Unlike the CNS and PNS. |
How do the endocrine glands control their hormone secretion? |
1.Negative feedback mechanism.
2.Neural Control. |
1. Negative feedback mechanism |
↓in Hormone level in Blood → ↑in secretion of Hormone → ↑in Hormone level in Blood → Result: Gland stops secreting Hormone (Works in a cycle!!)
Example:
↑in Glucose in Blood → ↑in secretion of Insulin → ↓in Blood Glucose level → Result: Pancreas stop secreting insulin.
|
2.Neural Control |
The release of hormones is controlled by the Hypothalamus of the brain which secretes substances called releasing factors. This stimulates glands to secrete their specific hormones.
Example: Growth Hormone Releasing Factor (GHRF) causes the pituitary to release growth hormones.
|
Endocrine Glands:
1.Pituitary Gland
(Hypophysis)
-Location |
Inferior surface of brain
Attached to Hypothalamus
Surrounded by the circle of Willis |
-Structure of Pituitary Gland |
Two Distinct Lobes:
1.Adenohypophysis
2.Neurohypophysis |
Adenohypophysis |
Anterior lobe.
Glandular Portion.
Produces and secretes six major hormones:
1.Growth Hormone(GH)
2.Thyroid-stimulating Hormone(STH)
3.Adrenocroticotropic Hormone(ACTH)
4.Follicle-stimulating Hormone(FSH)
5.Luteinizing Hormone(LH)
6.Prolactin |
1.Growth Hormone(GH) |
1.Increase protein synthesis and mitosis.
2.Regulates growth of most cells of the body. |
2.Thyroid-Stimulating Hormone(TSH) |
1.Regulates the hormonal activity of the thyroid gland. |
3.Adrenocroticotropic Hormone
(ACTH) |
1.Controls the secretions of the hormones of the arenal cortex. |
4.Follicle-Stimulating Hormone(FSH) |
1.Plays a role in ovulation.
2.Stimulates secretion of sex hormones.
-Estrogen and Testosterone |
5.Luteinizing Hormone(LH) |
1.Stimulates follicle(ova) develpoment in the ovary and sperm in the testes.
2.Also stimulates sex hormone secretion. |
6.Prolactin |
1.Plays a rolein the secretion of milk from mammary glands. "Lactation" |
Neurohypophysis |
Posterior Lobe.
Nervouos Portion.
Stores and releases 2 hormones produced by the Hypothalamus.
1.Oxytocin
2.Antidiuretic hormone (ADH) |
1.Oxytocin |
1.Stimulates uterine contractions.
2.Promotes milk ejections from breast. |
2.Antidiuretic Hormone(ADH) |
1.Affects permeability of the kidney tubules to reduce the excretion of water H2O.
2.Vasopressin: controls BP; constricts Blood Vessels. |
Functions of Pituitary Glands |
1."Master Glands" of the body.
2.Regulates many body activities through it's influence on other endocrine glands.
3.It does this by releasing specific hormones which affect the activity of these glands(eg. cause them to secrete the hormones they produce.) |
Thyroid Gland
-Location |
Anterior neck inferior to larynx.
Surrounds anterior and lateral aspects of the TRACHEA. |
Structure
(Gross) |
Two lobes connected by an Isthmus.
May contain a pyramidal lobe (superior extension) |
Structure
(Microscopic) |
1.Cuboidal Cells: hormone production
2.Follicles: store hormones |
Hormones |
1.Thyroxine(T4)
2.Triiodothyromine(T3)
3.Calcitonin |
Thyroxine(T4)
Triiodothyromine(T3)
-Site of Action
-Effect |
-Both found in most cells of the body
-Regulates Basal Metabolic Rate |
Calcitonin
-Site of Action
-Effect |
-Bone
-Regulates osteoclasts activity and therefore the amount of Ca which leaves bone → this lowers blood Ca level. |
Parathyroid Gland
-Location |
Embedded on posterior side of thyroid gland. |
Hormone |
Parathyroid hormone |
Parathyroid Hormone
-Site of Action
-Effect |
-Osteoclast in bone, kidney, intestine
-Increase blood calcium levels |
Adrenal Glands
-Location |
-Paired glands
-Located on superior poles of the kidneys. |
Structure |
1.Medulla
2.Cortex |
Medulla
-Structure
-Hormone |
-Inner portion
-activated by stress
-Prepares body for "Flight or Fight" reponse (ANS)
-Epinephrine |
Epinephrine(catecholamines)
-Site of Action
-Effect |
-Many organs and tissues
-Reinforces and prolongs Sympathetic ANS respons thus causes:
↑in Heart Rate!! and ↑in Respiration!! |
Cortex
-Structure
-Hormone |
-outer portion
-produces cortico hormones
-responds to ACTH(Adrenocorticotropic hormone)
-hormones:
1.Aldosterone
2.Cortisol/Hydrocortisone
3.Androgens |
Aldosterone
-General Info
-Site of Action
-Effect
(Primary and Secondary) |
-a mineralocorticoid
-kidney tubules
-Primary effect: regulates Na and K levels
-Secondary effect: to reabsorb water into tubules |
Androgens
(Estrogen and Progesterone)
-Site of Action
-Effect |
-Various tissues
-supplement gonadal hormones; promote development of secondary sex characteristics. |
Pancreas
-General Info
-Location |
-Pancreas are both exocrine as well as endocrine
-In the upper abdomen, posterior inferior to stomach |
What is the duct of the exocrine pancreas called?
and
What is the function of exocrine pancreas? |
-Duodenal Papilla
drains into the stomach
-containscells and ducts that produce and secrete digestive enzymes into the duodenum of the stomach. |
Structure of Endocrine Pancreas
Hormones |
-Islets of Langerhans contain endocrine cells.
-Hormones:
1.Insulin
2.Glucagon |
Insulin
-General Info(what cells produce insulin?)
-Site of Action
-Effect |
-Beta Cells produce insulin
-all body cells
-regulates transport of glucose into cells. |
Glucagon
-Genral Info(What cells produce this hormone?)
-Site of Action
-Effect |
-Alpha cells produce glucagon
-Liver
-promotes conversions of glucagon into glucose |
Gonads
Types |
-Ovary
-Testes |
Ovary
-Structure
-Hormones |
-corpus luteum and follicle
-Estrogen and Progesterone |
Estrogen and Progesterone
-Site of Action
-Effect |
-female reproductive organs esp. uterus
-development and regulation of female reproductive organs and secondary sex characteristics |
Testes
-Structure
-Hormones |
-Interstitial cells of leydig
-Testosterone |
Testosterone
-Site of Action
-Effect |
-Male reproductive organs
-Development and regulation of male reproductive organs and secondary sex characteristics. |
Pineal Gland
-Location |
-suspended from roof of 3rd ventricle |
Structure
Hormones |
-Glandular structure of epithelial cells.
-Melatonin |
What are the functions of Pineal Gland and Melatonin? |
-Receives and responds to input from visual pathway
-Highest level at night, may affect wake-sleep cycle(circardian rhythm)
-Inhibits hypothalamus stimulation of hormones which stimulate gonads. Delays sex maturation |