Lab # 1

Endocrine System

THIS IS A STUDY GUIDE, NOT AN ALL INCLUSIVE REVIEW.

THERE MIGHT BE THINGS NOT COVERED BY THIS STUDY GUIDE THAT MIGHT BE ASKED IN YOUR QUIZZES and PRACTICAL TESTS.

STUDENTS ARE RESPONSIBLE FOR STUDYING THEIR MANUAL AND FOR ALL THE MATERIAL COVERED DURING THE LABORATORY PERIOD, AS PER THE COURSE SYLLABUS

There are Two Organ Systems Dedicated to Maintaining the Internal Conditions (Homeostasis):

It employs electrical and chemical means to send messages from cell to cell.

1- Nervous System

2- Endocrine System It communicates by means of chemical messengers (hormones) secreted into to the blood.

Endocrine gland

Target cell (skeletal muscle cell)

Hormone

Target cell (skeletal muscle cell)

The Hypothalamus and the Pituitary GlandThe hypothalamus and the pituitary gland have the greatest influence in regulating the entire endocrine system.

Pituitary gland

Hypothalamus

Thalamus The hypothalamus secrets releasing hormones that trigger secretions of the anterior pituitary gland.The pituitary gland

secrets hormones that control other glands.

Corpus callosum Septum pellucidum Fornix

Pineal gland

Anterior commissure

Thalamus

Intermediate mass

Hypothalamus Mamillary bodyOptic chiasm

Pituitary gland

Epi- thalamus

Infundibulum

Three Mechanisms of Hypothalamic Control over Endocrine Function

Secretion of regulatory hormones to control activity of anterior lobe of pituitary gland

1

Production of ADH and Oxytocin2

Control of sympathetic output to adrenal medulla3

Tropic hormones secreted by anterior lobe of pituitary gland control other endocrine organs

Release of ADH and oxytocin

Secretion of epinephrine and norepinephrine

Anterior lobe or Adenohypophysis:

Anterior Posterior

Third ventricle of brain

Pars tuberalis (around the infundibulum)

Pars distalis(main portion of anterior lobe)

Infundibulum (stalk)

Posterior lobe, Neurohypophysis or Par nervosa

Hypothalamus:

Pars intermedia(in the interior)

Anatomy of the Hypothalamus and the Pituitary Gland

PRLProlactin (PRL)

After birth stimulates the mammary glands to synthesize milk.

Thyroid-stimulating hormone (TSH)

It stimulates secretion of thyroid hormone.

TSH

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Gonadotropins:

It stimulates the development of ovarian follicles, secretion of ovarian sex hormones, and sperm production.

It stimulates ovulation, stimulates corpus luteum to secrete progesterone, stimulates testes to secrete testosterone.

FSHLH

ACTH

It stimulates the adrenal cortex to secrete glucocorticoids.

Adrenocorticotropic hormone (ACTH)

GH

Liver

Fat,muscle,bone

It stimulates mitosis and cellular differentiation and thus promotes tissue growth throughout the body

Growth hormone (GH)

The Anterior Pituitary Produces Seven

Hormones

Releasing hormones are produced by the hypothalamus .

Releasing hormones target the anterior pituitary (adenohypo-physis )

Melanocyte stimulating hormone (MSH)

Releasing hormones

It stimulates the melanocytes of skin to produce melanin.

MSH

Oxytocin (OT)

Posterior pituitary or Neurohypophysis stores and

releases:

It stimulates uterine contractions and propulsion of semen.

It stimulates labor contractions during childbirth.

Antidiuretic hormone (ADH)

It increases water retention thus reducing urine volume and prevents dehydration.

It is also called vasopressin because it can cause vasoconstriction.

Oxytocin (OT)

Antidiuretic hormone (ADH)

Oxytocin (OT)

Antidiuretic hormone (ADH)

The Hypothalamus Produces two Hormones: Oxytocin (OT) and Antidiuretic Hormone

2- Thyroid Gland

Right lobe

Left lobe

Isthmus

T4 or Thyroxine

T3 or Triiodothyronine

Calcitonin

Thyroid Hormones

1- T4 or thyroxine

2- T3 or triioodothyronine

Follicular hormones (they are produced by the follicular cells)

1- They increase the rate of oxygen uptake and the basal metabolic rate

2- They enhance the effects of sympathetic stimulation (increasing heart rate, blood pressure, nervousness, and sweating)

3- They help to maintain body temperature

4- They help to regulate growth, development, and intracellular metabolism by increasing protein synthesis and lipid breakdown

5- They stimulate RBC formation, and speed up bone turnover

1- T4 or thyroxine

2- T3 or triiodothyronine

3- Calcitonin

3- Calcitonin

It is released in response to high levels of calcium in the blood

Calcitonin hormone is released by thyroid gland

Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix

[Calcium] in blood

[Calcium] in blood

3- Parathyroid Glands

Thyroid gland, posterior view

Parathyroid glands

Parathyroid glands

The Parathyroid Hormone

It increases calcium blood levels by targeting bone and kidneys

[Calcium] in blood

Parathyroid hormone is released by parathyroid gland

Stimulates the osteoclasts to resorb bone, releasing calcium to the blood

[Calcium] in blood

1- In bones

2- In kidneys

- It increases calcium reabsortion

- It increases formation and secretion of calcitriol Increases absorption of

calcium and phosphate from the intestines

[Calcium] in blood

4-Thymus GlandThe thymus is located in the mediastinum.It atrophies after puberty.The thymus is divided into two thymic lobes.Septa divide lobes into smaller lobules.

Functions:

T cells migrate into medulla. Mature T cells leave thymus by medullary blood vessels.

1- It secretes thymic hormones that stimulate stem cell divisions and T cell differentiation.

The lymphocytes divide in the cortex.

5- Suprarenal Glands

Mineralocorticoids(Aldosterone)

Glucocorticoids(Cortisol, Cortisone and

Corticosterone)

Sex hormones( androgens)

Medulla (It is considered part of Sympathetic Autonomic nervous System)

Catecholamines(Epinephrine and Norepinephrine)

Hormones of the Adrenal Cortex1- Mineralocorticoides (Aldosterone)

-It increases sodium and water reabsortion in kidneys

-It increases potassium secretion in kidneys

Aldosterone secretion is regulated by the renin-angiotencin mechanism

Blood pressure or plasma solute concentration

Renin-angiotencin mechanism

Aldosterone secretion

2- Glucocorticoids (Corticosterone and Cortisol)

-They help the body to resist stressors

-They depress the immune system and the inflammatory response

3- Gonadocorticoids or Sex Hormones (Androgens)

-They are masculinizing hormones. - In females they stimulate sexual drive. After menopause they are

converted to estrogens.

Blood Pressure

-Blood glucose levels

They increase:

-Cardiac activity

-Blood pressure

-Glycogen breakdown

-Triglyceride breakdown

Hormones of the Adrenal Medulla

Catecholamines(Epinephrine and Norepinephrine)

6- Pancreas

Endocrine pancreas Exocrine pancreas

Pancreatic acini

They secrete large quantities of an alkaline, enzyme rich fluid

1- Beta cells:

2- Alpha cells:

3- Delta cells:

4- F cells:

Insulin

Glucagon

Somatostatin

Pancreatic polypeptide

Islets of Langerhans

Pancreas

1- Glucagon (released by alpha cells)

Liver Blood glucose

2- Insulin (released by beta cells)

(beta cells) Insulin

- It increases the rate of glucose uptake by cells

- It increases cellular metabolism

- It increases the storage of lipid and glycogen

- Increases aminoacids absorption and protein synthesis

-It stimulates the liver to produce glucose

-It stimulates to breakdown glycogen

Glucagon

Blood glucose

Pancreas( alpha cells)

- Blood glucose

Blood glucose

Interstitial cells Sustentacular cellsThey produce Androgens

(testosterone) They produce Inhibin

Androgens: They promote maturation of male sexual organs, and production and maturation of sperm

Inhibin: It inhibits the secretion of FSH

The Testes Germ cellsThey become spermatozoa

7- Testes and Ovaries

The Ovaries

Primary oocytes

Primary follicles

Secondary follicles

Tertiary follicles

Corpus luteum :

Follicles: Estrogens

Progesterone

Prepares the uterus for implantation

Establishes the menstrual cycle

Maintains pregnancy

Prepares mammary glands for milk secretion

Stimulate development of the secondary sexual characteristics

Stimulate follicle maturation

Stimulate maturation of the female re[productive system

The Ovaries

7b- The Ovaries