NTA Level 4 • Semester 1 • PST04103

Structure and Functions of Endocrine System

Human Anatomy and Physiology • Source Session/Topic 32

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Session 32: Structure and Functions of Endocrine System

Total Session Time: 120 minutes+ 60 minutes assignment

Prerequisites

None

Learning Tasks

By the end of this session students are expected to be able to:

• Define the Endocrine System

• Explain the Structure of Endocrine System

• Explain the Functions of Endocrine System

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board, chalk and whiteboard markers

• Overhead projector (OHP) and computer

SESSION OVERVIEW

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing

STEP 2: Definition of Endocrine System (20 minutes)

• Endocrine system is the regulating system of the body by the chemical

substances called hormone, which are produced by endocrine glands

• The endocrine glands are ductless to sense that, they have no ducts to

take the hormones to specific sites

• Instead, hormones are secreted directly to the capillaries and

circulate in the blood throughout the body

• The hormones produced are divided in to three groups:

o Amines

▪ These simple hormones are structural variations of the amino acid

tyrosine

▪ Examples are thyroxine from thyroid gland), epinephrine and

norepinephrine (rom adrenal medulla)

o Proteins

▪ These hormones are chains of amino acids

▪ Examples are calcitonin from thyroid gland, insulin from the

pancreas, growth hormone from anterior pituitary gland

o Steroids

▪ These are hormones where by cholesterol is a precursor

▪ Examples are cortisol from adrenal cortex and oestrogen from the

ovaries.

STEP 3: Structure of Endocrine System (45 minutes)

|Activity: Small Group Discussion ( 30 minutes) |

| |

|DIVIDE students into small manageable groups |

| |

|ASK students to discuss on the following question |

| |

|What are the glands which form the endocrine system? |

| |

|ALLOW students to discuss for 15 minutes |

| |

|ALLOW few groups to present and the rest to add points not mentioned |

| |

|CLARIFY and SUMMARIZE by using the contents below |

• The endocrine system is the combination of endocrine glands which secrete

hormones

• The endocrine glands are:

o Pituitary gland

o Thyroid gland

o Parathyroid gland

o Adrenal gland

o Pancreas

o Ovaries

o Testes

Pituitary gland

• It hangs from the hypothalamus and is enclosed by the sphenoid bone

• It is divided into posterior pituitary gland and anterior pituitary

gland

o Posterior pituitary gland.

▪ The two hormones of the posterior pituitary gland are produced by

the hypothalamus and stored in the posterior pituitary gland until

needed

▪ These hormones are anti-diuretic hormone (vasopressin) and

oxytocin and both are peptides.

▪ Antidiuretic hormone increases the reabsorption of water by

kidney tubules, which decreases the amount of urine formed.

▪ The water is reabsorbed into the blood, so as urinary output is

decreased, blood volume is increased, which helps maintain normal

blood pressure

▪ Oxytocin stimulates contraction of the uterus at the end of

pregnancy and stimulates release of milk from the mammary glands.

o Anterior pituitary gland

▪ The hormones produced are regulated by releasing hormone from the

hypothalamus.

▪ The hormones produced are growth hormones (somatotropin), thyroid

stimulating hormone, adrenocorticotropic hormone, prolactin,

follicle stimulating hormone and luteinizing hormone.

▪ Growth hormones promote growth as increases amino acids transport

and protein synthesis.

▪ Thyroid stimulating hormone stimulates the normal growth of the

thyroid and the secretion of thyroxine (T4) and triiodothyronine

(T3).

▪ Adrenocorticotropic hormone (ACTH) stimulates the secretion of

cortisol and other hormones by the adrenal cortex.

▪ Secretion of ACTH is increased by corticotropin-releasing

hormone (CRH) from the hypothalamus.

▪ Prolactin is responsible for lactation. More precisely, prolactin

initiates and maintains milk production by the mammary glands.

▪ Follicle stimulating hormone stimulates the growth of ovarian

follicles; that is, it initiates egg development in cycles of

approximately28 days.

▪ Luteinizing hormone is responsible for ovulation, the release of

a mature ovum from an ovarian follicle.

Thyroid gland

• The thyroid gland is located on the front and sides of the trachea just

below the larynx

• The structural units of the thyroid gland are thyroid follicles, which

produce thyroxine (T4) and triiodothyronine(T3) and iodine is necessary

foe production of these hormones

o Thyroxine and T3

▪ Thyroxine (T4) and T3 have the same functions: regulation of

energy production and protein synthesis, which contribute to growth

of the body and to normal body functioning throughout life.

▪ Thyroxine and T3 increase cell respiration of all food types

(carbohydrates, fats, and excess amino acids) and thereby increase

energy and heat production.

o Calcitonin

▪ Decreases the reabsorption of calcium and phosphate from the

bones to the blood, thereby lowering blood levels of these

minerals.

▪ This function of calcitonin helps maintain normal blood levels of

calcium and phosphate and also helps maintain a stable, strong bone

matrix.

Parathyroid gland

• They produce a hormone called parathyroid hormone.

• Parathyroid hormone is an antagonist of calcitonin

• It increases the reabsorption of calcium and phosphate from bones to

the blood, thereby raising their blood levels. And also increase their

absorption from the intestine.

Pancreas

• It is located in the upper left quadrant of the abdominal cavity,

extending from the curve of the duodenum to the spleen.

• It is also an exocrine gland.

• The pancreatic hormones are produced by the cells called islet of

Langerhans and the hormones are insulin and glucagon.

• Glucagon stimulates the liver to change glycogen to glucose (this

process is called glycogen lysis, which literally means “glycogen

breakdown”) and to increase the use of fats and excess amino acids for

energy production.

• The overall effect of glucagon, therefore, is to raise the blood

glucose level and to make all types of food available for energy

production and is stimulated by hypoglycaemia.

• Insulin increases the transport of glucose from the blood into cells by

increasing the permeability of cell membranes to glucose.

• A deficiency of insulin or in its functioning is called diabetes

mellitus.

Adrenal glands

• The two adrenal glands are located one on top of each kidney.

• Each adrenal gland consists of two parts: an inner adrenal medulla and

an outer adrenal cortex.

• The cells of the adrenal medulla secrete epinephrine and

norepinephrine, which collectively are called catecholamine sand are

sympathomimetic.

• Epinephrine (Adrenalin) and norepinephrine (noradrenalin) are both

secreted in stress situations and help prepare the body for “fight or

flight.”

• The adrenal cortex secretes three types of steroid hormones:

mineralocorticoids, glucocorticoids and sex hormones (oestrogens and

androgens).

• Aldosterone is a mineralocorticoid and increases the reabsorption of

sodium and the excretion of potassium by the kidney tubules hence

maintains normal blood volume and blood pressure.

• Cortisol is a glucocorticoid and increases the use of fats and excess

amino acids (gluconeogenesis) for energy and decreases the use of

glucose

• It conserves glucose for use in brain

• Cortisol also has anti-inflammatory effect as they block the effects of

histamine

Ovaries

• The ovaries are located in the pelvic cavity, one on each side of the

uterus.

• The hormones produced by the ovaries are the steroids estrogen and

progesterone, and the protein inhibin.

• Estrogen promotes the maturation of the ovum in the ovarian follicle

and stimulates the growth of blood vessels in the endometrium (lining)

of the uterus in preparation for a possible fertilized egg

• Also estrogen is responsible for the development of female secondary

characteristics

• Progesterone promotes the storage of glycogen and the further growth of

blood vessels in the endometrium, which thus becomes a potential

placenta.

• Inhibin helps decrease the secretion of follicle stimulating hormone.

Testes

• The testes are located in the scrotum, a sac of skin between the upper

thighs

• Two hormones, testosterone and inhibin, are secreted by the testes.

• Testosterone promotes maturation of sperm in the seminiferous tubules

of the testes

• Testosterone is also responsible for development of male secondary

characteristics

• The function of inhibin is to decrease the secretion of FSH by the

anterior pituitary gland

• The interaction of inhibin, testosterone, and the anterior pituitary

hormones maintains spermatogenesis at a constant rate.

[pic]

Source: Scanlon,V.V., & Sanders,T (2007).

Figure 32.1a: Location of endocrine glands in the endocrine system

[pic]

Source: Scanlon,V.V., & Sanders,T (2007).

Figure 32.1b: Location of endocrine glands in the endocrine system

STEP 4: Functions of the Endocrine System (30 minutes)

|Activity: Buzzing (5 minutes) |

| |

|ASK students to pair up and buzz on the following question for 2 |

|minutes |

| |

|What are the functions of the endocrine system? |

| |

|ALLOW few pairs to respond and let other pairs to add on points not |

|mentioned |

| |

|WRITE their response on the flip chart/board |

| |

|CLARIFY and SUMMARIZE by using the content below |

The functions of the endocrine system include:

• The growth and repair of tissues

• The utilization of food to produce energy

• Responses to stress

• The maintenance of the proper levels and pH of body fluids

• The continuance of the human species all depend on hormones.

STEP 5: Key Points (5 minutes)

• The hormones of endocrine glands are involved in virtually all aspects of

normal body functioning

• The hormones may belong to amines, proteins or steroids

• The glands of the endocrine system includes pituitary gland, thyroid

gland, parathyroid gland adrenal gland, pancreas, ovaries and testes

STEP 6: Evaluation (5 minutes)

• What is endocrine system?

• What are the hormones secreted by the posterior and anterior pituitary

gland?

• What are the functions of testosterone?

Step 7: Assignment (10 minutes)

|Activity: Take Home Assignment (10 minutes) |

| |

|DIVIDE learners in groups or individual. |

| |

|ASK the learners to work on the following assignment |

| |

|Draw and label the endocrine glands in the endocrine system of a man |

| |

|ALLOCATE time for learners to do the assignment and submit |

| |

|REFER learners to recommended references |

References

Seeley, R. R., Stephens, T. D., &Tate, P. (2003). Anatomy and Physiology.

New York:

McGraw-Hill.

Shier, A., Butler, J., & Lewis, R. (2004). Hole’s Human Anatomy &

Physiology. New York:

McGraw-Hill.

Standring, S. (2008). Grays’s Anatomy The anatomical basis of clinical

practice. United

Kingdom: Churchill Livingstone Elsevier.

Thibodeau, G. A., & Patton, K. T. (1999). Anatomy & Physiology. Saint

Louis: Mosby, Von

Hoffman Press, Inc.

Waugh, A., & Grant, A. (2006). Ross and Wilson Anatomy and physiology in

Health and

illness. United Kingdom: Churchill Livingstone Elsevier.

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