Anatomy and Physiology of The Endocrine System

ATS Unit 5

Goals

• Discuss the anatomy of the endocrine system

• Identify and describe important hormones.

• Discuss how the endocrine system interacts with other systems in the body.

Endocrine System Basics

• The endocrine system includes all of the glands and tissues that produce hormones in our body.

– Hormones are chemical messages secreted directly into the blood stream that control and modify a huge number of bodily functions.

– The endocrine system is one of the two systems of communication in the body (the other is the nervous system).

Glands

• Glands are specialized tissues that excrete some substance. – Endocrine glands (also called ductless glands)

secrete chemicals inside of the body, directly into the blood stream.

– Other glands excrete substances outside the body or in the respiratory, digestive, urinary or reproductive tracts.

– Glands are commonly made of cuboidal epithelium.

Hormones

• Chemical messengers, similar to neurotransmitters, that act on tissue to elicit a targeted response. – From the Greek word for “excite”

– Three classes of hormones (based on chemistry)• Amines are derived from a single amino acid (epinephrine,

dopamine)

• Peptides are made of chains of amino acids, or proteins from 3 to over 200 (ghrelin, insulin)

• Steroids are made from cholesterol (fat based) and include androgens, estrogens, and glucocorticoids.

The Pituitary Gland

• Called the “Master Gland” because it releases many hormones that regulate other glands.

• Located just under the brain, and has an anterior and posterior lobe.

• It communicated regularly with the hypothalamus (a part of the brain that monitors physiological status, content of blood, etc.) and can adjust these factors as needed.

Hormones of the Pituitary Gland

Anterior

• Growth Hormone

• Prolactin

• Thyroid Stimulating Hormone

• Adrenocorticotropic Hormone

• Follicle Stimulating Hormone

• Luteinizing Hormone

Posterior

• Vasopressin (Antidiuretic Hormone)

• Oxytocin

Melanocyte Stimulating Hormone is release by cells in-between the lobes

The Thyroid

• Butterfly Sharped and located in the neck, this gland releases three hormones: – Thyroxine and Triodothyronine: work together to

control rate of glucose and oxygen metabolism, protein synthesis, and break down of stored energy.

– Calcitonin: regulates amount of Calcium in blood by stimulating osteoblasts to add calcium to bone, therefore lowering the blood levels.

The Parathyroid Glands

• These are tiny glands located on either side of the thyroid. They only produce one hormone. – Parathyroid Hormone has one job,

which is to increase blood levels of calcium. It does this in 2 ways: • Stimulates osteoclast to release calcium

from bone.

• Reduce the amount of calcium eliminated by the kidneys.

Adrenal Glands

• Two glands (each two glands in one) that sit on top of each kidney They are controlled by the adrenocorticotropic hormones from the pituitary.

Hormones of the Adrenal Glands

Cortex

• Mineralocorticoids (esp. Aldosterone) which help regulate the levels of electrolytes in the blood stream (mostly potassium and sodium)

• Glucocorticoids (cortisone and cortisol) that increase the levels of glucose on the blood.

• Androgens, which are similar to male sex hormones but are in both genders.

Medulla

• Epinephrine, hormone of the sympathetic nervous system. Increase respiratory rate cardiac output, metabolism, etc..

• Norepinephrine works with epinephrine, increased vascular tone and improves focus and concentration.

Gonads

Ovaries

• These produce estrogen and progesterone which stimulate female sex characteristics and the monthly cycle.

• They respond to FSH and LH from the anterior pituitary gland.

Testes

• Testosterone develops the male sex organs and secondary sex characteristics.

• They respond to LH from the anterior pituitary gland.

Pancreas

• While most of the pancreas serves to provide digestive enzymes, small clusters of cells serve as an endocrine gland. – Islets of Langerhans:

• produce insulin which has 4 jobs:– Facilitates transport on glucose into cells

(lowering blood levels)– Promotes fatty acid transport into cells. – Promotes amino acid transport into

cells. – Stimulates protein synthesis.

• Make Glucagon– Works as the opposite of insulin and

increases blood glucose by releasing it from liver.

Pineal Gland

• Located in the third ventricle of the brain, this tiny gland makes Melatonin.

– Melatonin drops body temperature and has some relationship to the sleep-wake cycle.

– Release is stimulated by light levels detected by eyes.

Hormones Produces Elsewhere

• Prostaglandins are released by many tissues in the body, and activity depends on their origin. Generally, they act to constrict or relax blood vessels and cause muscle contracts as in labor.

• Neurohormones are released in the brain that travel to the body tissues. For example, the hypothalamus sends messengers to the pituitary gland.

• Leptin is produces by fat cells to suppress appetite.

• Ghrelin is mad in the stomach and stimulates appetite.

Control of Hormones

• Release and action of hormones typically follow a negative feedback loop (review).

• Many hormones work as antagonistic pairs that regulate the same function.

• Hormones and glands are also controlled by the nervous system which can control by direct monitoring and response, or indirectly by emotional or situational triggers.