Definition : System of glands. A gland is a group of
cells that produces and secretes, or gives off chemicals
directly into the bloodstream. These chemicals called
hormones can be transported to other parts of the body
where they influence cells, organs, and functions of our
bodies
Hypothalamus
Pituitary Gland
Pineal Gland
Thymus
Thyroid Gland
Parathyroid Gland
Pancreas
Adrenal Glands
Ovaries
Testes
Placenta
Gastrointestinal Mucosa
Secretes: - Thyrotropin-releasing hormone (TRH) that causes the
anterior pituitary to secrete TSH
- Prolactin-releasing hormone (PRH ) that causes the
anterior pituitary to secrete PRL
- Dopamine (Prolactin-inhibiting hormone) to inhibit
prolactin release from the anterior pituitary gland
- Growth hormone-releasing hormone (GHRH) that
causes the anterior pituitary to secrete GH
- Somatostatin/Growth hormone-inhibiting hormone
(GHIH) that inhibits GH and thyroid-stimulating hormone (TSH)
release from the anterior pituitary gland
- Gonadotropin-releasing hormone GnRH or
LHRH that causes the anterior pituitary to secrete LH
- Gonadotropin-releasing hormone GnRH or
FSHRH that causes the anterior pituitary to secrete FSH
- Corticotropin-releasing hormone CRH that
causes the adrenal cortex to secrete glucocorticoids
- Controls body temperature, hunger, moods,
sex drive, sleep and thirst
Produces the serotonin derivative melatonin, a
hormone that affects the modulation of wake/sleep
patterns and seasonal functions
Anterior Lobe : - GH (causes bones and muscular growth)
- ACTH (stimulates the adrenal cortex to
secrete the glucocorticoids hormones)
- TSH (stimulates the thyroid to secrete the
hormones thyroxine/T4, Triiodothyronine/ T3)
- FSH (stimulates spermatogenesis and
oogenesis)
- LH (Causes ovulation and the production of
testosterone)
- PRL (stimulates the mammary glands to
produce milk)
- MSH (stimulates the production of melanin)
Posterior Lobe : - ADH/Vasopressin (Stimulates the
reabsorption of water by the kidneys)
- Oxytocin (stimulates the uterus to
contract during labor and childbirth as well as the
release of milk from the mammary glands)
Located anterior to the trachea
Secretes Thyroxine/T4 that regulates the BMR and
affects growth and development, body temperature,
and heart rate
Transforms T4 into Tri-iodothyronine/T3 that has
more effect on the body than T4
Secretes Calcitonin that reduces the level of calcium
in the blood
They are 4 glands located around the dorsal and lower
sides of the thyroid gland
Secrete Parathyroid hormone/PTH that increases the
level of calcium in the blood to reach normal range
when the calcium level in the blood goes down
Located behind the stomach across the back of the abdomen with the head connected to the duodenum through the pancreatic duct
Islets of Langerhans divided into the alpha(α), beta(β) and delta (∆) cells
The alpha cells secrete glucagon that increase the glucose level in the blood
The beta cells secrete insulin that decreases the glucose level in the blood so that the normal fasting blood glucose level is 70-100mg/dl
The delta cells secrete somatostatin that inhibit the secretion of insulin, glucagon and many other hormones
Adrenal Cortex secretes : - Cortisol (increases blood sugar level and reduces inflammation)
- Corticosterone (increases blood
sugar level)
- Aldosterone (regulates
electrolytes and water balance by reabsorbing sodium and
chloride and excreting potassium)
- Androgens (Testosterone,
Dehydroepiandrosterone (DHEA), Androstenedione (Andro),
Androstenediol, Androsterone, Dihydrotestosterone (DHT)
Adrenal Medulla secretes : - Dopamine
- Epinephrine (also known
as adrenaline is responsible for the fight or flight
syndrome. Regulated by the sympathetic nervous
system)
- Norepinephrine (increases
the heart rate, cardiac output and level of glucose in the
blood)
Secretes Progesterone : - Prepares the uterus for pregnancy
Secretes Estrogen : - Causes the repair of the endometrium after the menses
- Causes the following secondary sexual
characteristics → Enlargement of breasts and erection of
nipples
→ Growth of body hair especially underarm
and pubic areas
→ Fat deposits mainly around the buttocks, thighs
and hips
→ Smaller waist, hands and feet than men
→ Widening of hips and greater development of
thigh muscles behind the femur
Secretes testosterone: - Necessary for the maturation of sperm to occur
- That causes the following secondary
sexual characteristics → Growth of facial hair and body hair
(chest, underarm, abdominal and pubic areas)
→ Enlargement of larynx (Adam's apple)
and deepening of voice
→Increased muscle mass and strength
and secretions of oil and sweat glands often causing acne
and body odor
→ Enlargement of the penis
→ Broadening of shoulders (wider than
hips) and chest
→ Coarsening or rigidity of skin texture
due to less subcutaneous fat
→ Larger hands and feet than women
→ Greater mass of thigh muscles in
front of the femur
→ Smaller and wider waist than females
→ On average heavier skull and bone
and taller than adult females
Secretes Human Chorionic Gonadotrophin hormone
(HCG), estrogen and progesterone that help during
pregnancy
Mucosae of the stomach, pancreas and duodenum secrete
gastrin : - Stimulates Gastric acid secretion in the
stomach
Mucosa of the duodenum secretes Secretin :- Stimulates
the pancreas to release pancreatic juice to reduce the
acidity of the gastric juice in the small intestine
Mucosa of the duodenum secretes Pancreozymin-
cholecystokinin : - Stimulates the contraction of the
gallbladder and the secretion of pancreatic juice
Addison’s Disease : Decreased production of the
adrenocortical hormones caused by autoimmune
disease or infections or cancer or hemorrhage in the
adrenal glands. Causes weakness, lethargy,
hypoglycemia, vomiting, diarrhea, increased
pigmentation of the skin etc…
Diabetes Mellitus : - Pancreas does not produce enough
insulin causing high blood sugar level (Type 1
diabetes)
- Insulin is unable to help the
glucose get into the cells in the body (type 2 diabetes).
Type 2 diabetes happens in adults and pregnant women
Gigantism : Hypersecretion of GH during childhood before the closure of the bone growth plates
Robert Wadlow, the tallest man known to have lived
(8 ft 11 in) with his father, Harold Wadlow (5 ft 11 1/2 in)
Hypothyroidism : Hyposecretion of thyroid hormones
Examples are Hashimoto’s thyroiditis and Myxedema