The Endocrine SystemINTRODUCTION TO HUMAN GROWTH AND DEVELOPMENT

What is the endocrine system?• It includes all of the glands of the body and the

hormones produced by those glands.• These glands regulate the function of organs in the body and

therefore help to maintain the body’s homeostasis.

• These functions include: cellular metabolism, reproduction, sexual development, sugar and mineral homeostasis, heart rate and digestion.

What are hormones?• Hormones are a chemical messenger that are released

into the blood stream. They control many of your body’s activities

• Gland = a group of cells or an organ that secretes hormones

The Hypothalamus• Location: In the brain, inferior to the thalamus

• Purpose: It is responsible for the direct control of the endocrine system through the pituitary gland.• All of the releasing and inhibiting hormones affect the function of

the pituitary gland

The Eight Endocrine Glands• Which do you remember?

1. Pituitary Gland

2. Pineal Gland

3. Thyroid Gland

4. Parathyroid Gland

5. Adrenal Glands

6. Pancreas

7. Ovaries/Testes

8. Thymus Gland

The Pituitary Gland• Location: Small pea-sized

lump of tissue connected to the hypothalamus

• Purpose: It produces 6 important hormones and is controlled by the releasing and inhibiting hormones of the hypothalamus. Produces hormones that control other glands and that control the growth of bones and the movement of smooth muscles

The Pineal Gland• Location: Pinecone

shaped mass found just posterior to the thalamus of the brain

• Function: Produces the hormone melatonin which helps to regulate the sleep-wake cycle

The Thyroid Gland• Location: Butterfly

shaped gland located at the base of the neck

• Function: Produces the hormone thyroxin which controls metabolism

The Parathyroid Gland• Location: 4 small masses

located on the thyroid gland

• Function: Regulates calcium and phosphorus in the body

The Adrenal Gland• Location: Triangular

glands found near the kidneys

• Function: Send fight or flight response to the brain and also contains small amounts of testosterone that may help with secondary male sex characteristics. It also controls the body’s water balance

The Pancreas• Location: In the

abdominal cavity

• Function: Produces glucagon which is responsible for raising blood glucose levels. It also produces insulin which is responsible for lowering blood glucose levels

The Testes• Location: Found in the

scrotum of males

• Function: Produces the androgen testosterone after the start of puberty which effects the muscles, bones, sex organs and hair follicles.• Puberty occurs in males

usually between the ages of 12 and 15

The Ovaries• Location: Almond shaped

glands in the pelvic cavity

• Function: Produces the female sex hormone progesterone and estrogen. Progesterone is most active in females during pregnancy and ovulation. Estrogen causes female secondary sex characteristics• Puberty occurs in females

usually between the ages of 8 and 15

The Thymus• Location: Triangular

shape organ found in chest

• Function: Helps protect the body from pathogens. Becomes inactive during puberty and is slowly replaced by adipose tissue.

The Female Reproductive SystemA BRIEF OVERVIEW

About the Female Reproductive System• Organs Include: Ovaries, Fallopian Tubes, Uterus and

Vagina• The ovaries produce egg cells (ova/ovum) and estrogen

• Each ovum is enclosed in a small hollow ball called a follicle

• A female is born with 200,000 to 250,000 immature egg cells and only 400 of them will mature in her lifetime

During Puberty…• The egg cells begin to

develop and each month one egg matures and is released from its follicle (called ovulation) and is part of the menstrual cycle

• The menstrual cycle is associated with hormone production and ovulation

Process Continued• The egg is released from

the ovaries and enters the Fallopian Tube into the Uterus• Once in the Fallopian Tube

one of two things can happen1. The egg disintegrates or

leaves the body during the menstrual flow

2. If sperm are present when an egg moves through the fallopian tube conception or fertilization may occur

The Male Reproductive SystemA BRIEF OVERVIEW

External Male Organs1. The Penis - Used for reproduction and urination. The

reproductive function is to deposit sperm into the vagina

2. The Scrotum – Sac like pouch that holds each testis and helps regulate the temperature for sperm production. It hangs lower from the body so that the testes have a lower temperature than the rest of the body which allows for the production of sperm.

Internal Male Organs1. Testes – Male

reproductive glands that produce sperm cells and testosterone

• Seminiferous Tubules – Network of coiled tubes inside the testes which produces sperm

2. Epididymis – Where sperm pass after they are produced and are stored

Internal Male Organs Cont.3. Vas Deferens – The

epididymis leads to the Vas Deferens which are thin tubes that are a passageway for sperm and storage for sperm

4. Seminal Vesicles – Two small glands that secrete a fluid that nourishes and helps the sperm move

Internal Male Organs Cont.5. Prostate Gland – A gland

that makes a fluid to help keep sperm alive

6. Cowper’s Glands – Glands that secrete a clear, lubricating fluid

After Sperm are Produced• Two options

1. Sperm will be stored in the body

2. Sperm will leave the body through ejaculation which is a series of muscular contractions.

• Semen is a fluid that consists of the combination of sperm, fluids from the seminal vesicles, prostate gland and Cowper’s glands.