The-Endocrine-System.pptx Anatomy and Physiology

Intended Learning Outcome:
1. Explain the general functions of the endocrine system.
2. Describe the anatomy and functions of endocrine organs.
3. Analyze the processes of hormone secretion and regulation.
4. Discuss the role of hormones in maintaining homeostasis.
5. Identify common endocrine disorders and their impact on
physiological function.

Introduction to the Endocrine
System
• The endocrine system, alongside the nervous system, regulates body activities.
• While the nervous system acts through electrical impulses for short-duration effects, the endocrine
system uses chemical messenger called hormones for longer-lasting effects.
• Hormones influence growth, development, and metabolic activities over minutes, hours, or weeks.
Types of Glands:
1. Exocrine Glands:
• Have ducts that carry secretions to surfaces.
• Examples include sweat, sebaceous, mammary glands, and digestive glands.
2. Endocrine Glands:
• Ductless glands.
• Derived from "endo" (within) and "krine" (to separate or secrete).
• Secrete hormones directly into the bloodstream.

Chemical Nature of Hormones
• Hormones are classified as amino acid, proteins or steroids.
• Except for sex hormones and those from the adrenal cortex, most
human hormones are proteins or protein derivatives.

Mechanisms of Hormone Synthesis,
Storage, and Release
• Humoral Stimuli: This mechanism controls hormone release in
response to changes in extracellular fluids like blood.
• Hormonal Stimuli: Hormonal stimuli involve the release of a
hormone in response to another hormone.
• Neural Stimuli: In some cases, the nervous system directly stimulates
endocrine glands to release hormones.

Major Endocrine Glands
• The endocrine system consists of eight major glands spread
throughout the body.
• Some glands have non-endocrine regions with functions
beyond hormone secretion:
• Pancreas: Contains an exocrine portion for digestive
enzyme secretion and an endocrine portion for hormone
secretion.
• Ovaries and testes: Produce hormones and also generate
ova and sperm.
• Certain organs like the stomach, intestines, and heart do
produce hormones, but hormone secretion is not their
primary function.

Pituitary Gland
Location and structure
• The pituitary gland, also known as the hypophysis, is
approximately 1 centimeter in diameter, resembling the
size of a pea.
The gland comprises two distinct regions
• Anterior lobe (adenohypophysis)
• Posterior lobe (neurohypophysis)
• The activity of the adenohypophysis is regulated by releasing
hormones released by the hypothalamus.
• Conversely, the neurohypophysis is governed by nerve
stimulation.

Pituitary Gland
Hormones of the Anterior Lobe (Adenohypophysis)
1.Growth Hormone (GH):
Stimulates bone, muscle, and organ growth by promoting protein
synthesis.
• Insufficient GH in children may lead to pituitary dwarfism, while
excess GH can cause gigantism.
2.Thyroid-Stimulating Hormone (TSH):
• Induces the thyroid gland to secrete thyroid hormone.
• Hypersecretion of TSH can cause thyroid enlargement and excess
thyroid hormone production.
3.Adrenocorticotropic Hormone (ACTH):
• Stimulates the adrenal cortex to secrete cortisol and other cortical
hormones.
4.Gonadotropic Hormones:
• Act on the gonads (ovaries and testes) to regulate their
development, growth, and function.
5.Prolactin:
• Promotes glandular tissue development in the female breast during
pregnancy and stimulates milk production postpartum.

Pituitary Gland
Hormones of the Posterior Lobe (Neurohypophysis):
1.Antidiuretic Hormone (ADH):
• Enhances water reabsorption by kidney tubules, reducing
water loss in urine.
• Inadequate ADH leads to excessive water loss through
urine.
2.Oxytocin:
• Causes uterine smooth muscle contraction.
• Stimulates milk ejection from lactating breasts.

Pineal Gland
Location and Structure:
• Situated posteriorly from the third ventricle of the brain.
• Appears as a small cone-shaped structure.
• Composed of neurons, neuroglial cells, and specialized secretory
cells known as pinealocytes.
Hormones
1. Melatonin:
• Synthesized by Pinealocytes
• It is secreted directly into the cerebrospinal fluid.
• It is then transported into the bloodstream.
• Influences reproductive development.
• Regulates daily physiologic cycles, including the sleep-wake
cycle.
• Plays a role in circadian rhythm regulation and the body's
response to light and darkness.

Thyroid Gland
Location and structure:
• Situated in the neck.
• Consists of two lobes connected by an isthmus.
Hormones
1. Thyroxine (T4):
• Regulates metabolism by influencing the rate at which cells burn fuels from
food to produce energy.
• Supports normal growth and development, particularly in children.
2. Triiodothyronine (T3):
• Works synergistically with thyroxine to regulate metabolism and energy
production.
• Helps regulate body temperature, heart rate, and other vital functions.
3. Thyroid-Stimulating Hormone (TSH):
• Stimulates the thyroid gland to produce and release thyroxine (T4) and
triiodothyronine (T3) into the bloodstream.
• Plays a key role in maintaining thyroid hormone levels within the body.
4. Calcitonin:
• Regulates calcium levels in the blood by inhibiting the breakdown of bone
and promoting calcium deposition in bone tissue.
• Counteracts the action of parathyroid hormone to prevent hypercalcemia.

Parathyroid Gland
Location and Structure
• Location: Four small masses of epithelial tissue are embedded in the connective tissue
capsule on the posterior surface of the thyroid glands.
• Structure: The parathyroid glands are typically found on the posterior aspect of the
thyroid gland, arranged in pairs. They consist of epithelial cells surrounded by a
fibrous capsule.
Hormones
1. Parathyroid Hormone (PTH) or Parathormone:
• This hormone is secreted in response to low blood calcium levels. It acts on the bones,
kidneys, and intestines to increase calcium levels in the blood.
• PTH plays a crucial role in regulating calcium levels in the blood. It increases calcium
release from bones, enhances calcium reabsorption in the kidneys, and stimulates the
production of activated vitamin D, which increases calcium absorption in the
intestines.
Associated Conditions
• Hypoparathyroidism: Insufficient secretion of PTH leads to hypoparathyroidism,
resulting in low blood calcium levels. This condition can lead to increased nerve
excitability, causing symptoms such as muscle cramps, spasms, and seizures.

Adrenal Gland
• Paired glands located near the upper portion of each kidney.
• Divided into an outer cortex and an inner medulla. The cortex and medulla develop from different
embryonic tissues and secrete different hormones.
Hormones
Adrenal Cortex:
1. Mineralocorticoids:
• Secreted by the outermost region, mainly aldosterone, which regulates sodium and water
balance.
2. Glucocorticoids:
• Secreted by the middle region, primarily cortisol, which regulates glucose metabolism and
has anti-inflammatory effects.
3. Gonadocorticoids:
• Secreted by the innermost region, including minimal amounts of male and female sex
hormones (androgens and estrogens).
Adrenal Medulla:
4. Epinephrine and Norepinephrine:
• Secreted in response to sympathetic nerve stimulation, especially during stressful situations.
They enhance the body's response to stress.

Pancreas
• Location: Transversely positioned along the posterior abdominal wall,
posterior to the stomach, extending from the duodenum to the spleen.
• Structure: Divided into an exocrine portion that secretes digestive enzymes
and an endocrine portion consisting of pancreatic islets.
Hormones
1. Glucagon:
• Secreted by alpha cells in response to low blood glucose levels.
• It increases blood glucose levels by promoting glycogenolysis and
gluconeogenesis in the liver.
2. Insulin:
• Secreted by beta cells in response to high blood glucose levels.
• It decreases blood glucose levels by promoting cellular uptake of
glucose, glycogenesis, and lipogenesis.
Associated Conditions:
• Hypofunction: Insufficient insulin secretion can lead to hyperglycemia and
diabetes mellitus.
• Hyperfunction: Excessive insulin secretion may cause hypoglycemia and
related symptoms.

Gonads (Male Reproductive
System)
• The male gonads, known as testes, are located within the scrotum.
• They are responsible for producing sperm and secreting hormones.
Testes
• The testes consist of seminiferous tubules where spermatozoa are produced and
interstitial cells (Leydig cells) that secrete testosterone.
Hormones
1. Testosterone:
• Secreted by Leydig cells in the testes, testosterone is the primary androgen
hormone in males.
• It is involved in the development of male reproductive structures, secondary
sexual characteristics, and the maintenance of reproductive function.
• Hypofunction: In males, hypofunction of the testes can lead to decreased
testosterone production, resulting in symptoms like decreased libido, infertility, and
muscle weakness.
• Hyperfunction: Excessive testosterone secretion in males can lead to conditions like
precocious puberty, masculinization in females (virilization), and an increased risk
of prostate enlargement and cancer.

Gonads (Female Reproductive
System)
• The female gonads, known as ovaries, are situated within the pelvic cavity.
• They are responsible for producing ova and secreting hormones.
Ovaries:
The ovaries consist of follicles that contain ova and stroma tissue.
Hormones
1. Estrogen:
• Produced by ovarian follicles in females, estrogen is a group of steroid hormones
responsible for the development of female secondary sexual characteristics,
regulation of the menstrual cycle, and maintenance of reproductive organs.
2. Progesterone:
• Secreted by the corpus luteum in the ovaries, progesterone prepares the uterine
lining for implantation and maintains pregnancy.
Hypofunction: In females, ovarian hypofunction may cause menstrual irregularities,
infertility, and symptoms of estrogen deficiency like hot flashes and vaginal dryness.
Hyperfunction: Excessive estrogen or progesterone secretion in females may result in
menstrual irregularities, breast tenderness, and other symptoms associated with
hormonal imbalance.

Other endocrine glands
Thymus
• The thymus gland is situated in the upper chest, just beneath the
breastbone.
Hormone
1. Thymosin:
• Plays a crucial role in the development and maturation of T-
lymphocytes, which are essential for the body's immune response.
Stomach
• The stomach is a muscular organ located in the upper abdomen.
Hormone
1. Gastrin:
• Stimulates the production of hydrochloric acid and the enzyme
pepsin, aiding in the digestion of food.

Small Intestine
• The small intestine is a long, coiled tube located in the abdominal cavity, following
the stomach.
Hormones
1. Secretin:
• Stimulates the pancreas to produce a bicarbonate-rich fluid that neutralizes stomach
acid.
2. Cholecystokinin:
• Stimulates the contraction of the gallbladder, releasing bile, and also prompts the
pancreas to secrete digestive enzymes.
Heart
• The heart is a muscular organ located in the chest cavity, between the lungs.
Hormone
1. Atrial natriuretic hormone (ANP):
• Also known as atriopeptin, it helps regulate blood pressure and electrolyte balance
by promoting sodium and water excretion by the kidneys.

Placenta
• The placenta is an organ that develops during pregnancy, attached to
the uterine wall, providing nourishment and oxygen to the developing
fetus.
Hormone
1. Human chorionic gonadotropin (hCG):
• Signals the mother's ovaries to continue producing hormones necessary
to sustain the uterine lining, preventing menstruation and supporting
the pregnancy.

1.Metabolism
• Hormones like insulin regulate glucose metabolism.
2. Growth and Development
• Growth hormone influences growth and development.
3. Reproduction
• Sex hormones control reproductive functions.
4. Stress Response
• Adrenal hormones regulate the body's response to stress.
5. Electrolyte Balance
• Hormones like aldosterone maintain electrolyte balance
Roles of Hormone in
Homeostasis

Review/Summary
• Chemical messengers from the endocrine system help regulate body
activities. Their effect is of longer duration and is more generalized than
that of the nervous system.
• Neurons are the nerve cells that transmit impulses. Supporting cells are
neuroglia.
• Endocrine glands secrete hormones directly into the blood, which
transports the hormones through the body.
• Cells in a target tissue have receptor sites for specific hormones.
• Many hormones are regulated by a negative feedback mechanism; some
are controlled by other hormones; and others are affected by direct nerve
stimulation.
• Even though the endocrine glands are scattered throughout the body, they
are still considered to be one system because they have similar functions,
similar mechanisms of influence, and many important interrelationships.
• Major glands include: pituitary gland, thyroid gland, parathyroid gland,
adrenal (suprarenal) gland, pancreas, gonads (testes and ovaries), pineal
gland, and other endocrine glands.

The-Endocrine-System.pptx Anatomy and Physiology

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