Human Glands and Endocrine System

Release substances through ducts to external surfaces or cavities, rather than into the bloodstream.
Major exocrine glands include:
- Salivary Glands: Produce saliva for digestion.
- Sweat Glands: Help regulate body temperature and eliminate waste.
- Sebaceous Glands: Produce oil (sebum) for skin lubrication.
- Mammary Glands: Produce milk in females for feeding infants.
- Pancreatic Exocrine Tissue: Releases digestive enzymes into the small intestine.

Hormone levels are regulated through feedback mechanisms:
- Negative Feedback: The output reduces the initial stimulus (e.g., high blood sugar induces insulin release, which lowers blood sugar).
- Positive Feedback: The output enhances the initial stimulus (e.g., oxytocin during childbirth).
Hormones can be categorized by:
- Peptide Hormones: Chains of amino acids (e.g., insulin).
- Steroid Hormones: Derived from cholesterol (e.g., cortisol).
- Amine Hormones: Derived from single amino acids (e.g., adrenaline).
Regulation involves complex interactions among various hormones and biological signals to maintain homeostasis.

The endocrine system is composed of glands that release hormones directly into the bloodstream.
Major glands include the pituitary gland, thyroid gland, adrenal glands, pancreas, and gonads (ovaries and testes).
The pituitary gland, located at the base of the brain, is often called the "master gland" because it regulates the function of other glands.
The thyroid gland, located in the neck, regulates metabolism, growth, and development.
The adrenal glands, located on top of each kidney, produce hormones like cortisol and adrenaline.
The pancreas functions as both an endocrine and exocrine gland; it regulates blood sugar levels by producing insulin and glucagon.
The gonads produce sex hormones and are involved in reproduction.

Exocrine glands release substances through ducts to external surfaces or cavities, rather than into the bloodstream.
Major exocrine glands include salivary glands, sweat glands, sebaceous glands, mammary glands, and pancreatic exocrine tissue.
Salivary glands produce saliva for digestion.
Sweat glands help regulate body temperature and eliminate waste.
Sebaceous glands produce oil (sebum) for skin lubrication.
Mammary glands produce milk in females for feeding infants.
Pancreatic exocrine tissue releases digestive enzymes into the small intestine.

Hormone levels are regulated through feedback mechanisms, primarily negative feedback and positive feedback.
Negative feedback occurs when the output of a hormone reduces the initial stimulus, like high blood sugar inducing insulin release, which lowers blood sugar.
Positive feedback occurs when the output of a hormone enhances the initial stimulus, like oxytocin release during childbirth, which amplifies labor contractions.
Hormones are categorized into three classes: peptide hormones, steroid hormones, and amine hormones.
Peptide hormones are chains of amino acids, like insulin.
Steroid hormones are derived from cholesterol, like cortisol.
Amine hormones are derived from single amino acids, like adrenaline.
Regulation involves complex interactions among various hormones and biological signals to maintain homeostasis.

Pituitary gland: Often referred to as the "master gland" due to its role in regulating other endocrine glands.

Pancreas: A key exocrine gland that produces digestive enzymes aiding in food breakdown.

Steroid hormones: Derived from cholesterol, a prominent example being cortisol which plays a vital role in stress response.

Negative feedback: A common regulatory mechanism in the endocrine system. High blood sugar levels stimulate insulin release, which in turn lowers blood sugar, illustrating this principle.

Thyroid gland: Produces hormones that regulate metabolism, growth, and development.

Exocrine glands: Release their secretions through ducts, often directly onto target tissues. Think of sweat glands or salivary glands.
Endocrine glands: Release hormones directly into the bloodstream, where they travel to target tissues for action.

Hormones: Chemical messengers produced by endocrine glands, influencing various bodily functions.

Several factors can influence hormone secretion from endocrine glands, including:
- Hormonal stimulation: One hormone triggering the release of another.
- Neural stimulation: Nerves triggering hormone release.
- Chemical changes in the blood: Fluctuations in blood glucose or calcium levels stimulating hormonal responses.

Exocrine glands: Do not directly participate in hormone regulation.
Endocrine glands: Specialized to produce and release hormones into the bloodstream.

Receptor-mediated action: Hormones typically exert their effects by binding to specific receptors on target cells, triggering intracellular changes.