Human Anatomy - Endocrine System PDF

# The Endocrine System - Second-messenger system of the body. - Uses chemical messengers (hormones) that are released into the blood. - Hormones control several major processes: - Reproduction - Growth and development - Mobilization of body defenses - Maintenance of much of homeo...

# The Endocrine System - Second-messenger system of the body. - Uses chemical messengers (hormones) that are released into the blood. - Hormones control several major processes: - Reproduction - Growth and development - Mobilization of body defenses - Maintenance of much of homeostasis. - Regulation of metabolism. # Hormone Overview - Hormones are produced by specialized cells. - Cells secrete hormones into extracellular fluids. - Blood transfers hormones to target sites. - These hormones regulate the activity of other cells # Major Endocrine Organs - Pituitary gland - Thyroid gland - Parathyroid glands - Adrenal glands - Pineal gland - Thymus gland - Pancreas - Gonads (Ovaries and Testes) - Hypothalamus # Location of Major Endocrine Organs - Diagram of a human body, highlighting the location of each endocrine organ. # Pituitary Gland - Size of a pea - Hangs by a stalk from the hypothalamus in the brain. - Protected by the sphenoid bone. - Has two functional lobes: - Anterior Pituitary - glandular tissue - Posterior Pituitary - nervous tissue - Often called the "master endocrine gland". # Hormones of the Anterior Pituitary - Six anterior pituitary hormones - Two affect non-endocrine targets - Growth hormone - Prolactin - Four stimulate other endocrine glands (tropic hormones) - Thyroid-stimulating hormone (thyrotropic hormone) - Adrenocorticotropic hormone - Two gonadotropic hormones - Diagram, showing the anterior pituitary gland and the hormones it produces, along with their targets. # Hormones of the Anterior Pituitary - Growth hormone - General metabolic hormone - Major effects are directed to the growth of skeletal muscles and long bones - Plays a role in determining final body size - Causes amino acids to be built into proteins - Causes fats to be broken down for a source of energy # Hormones of the Anterior Pituitary - Growth hormone (GH) disorders - Pituitary dwarfism results from hyposecretion of GH during childhood. - Gigantism results from hypersecretion of GH during childhood. - Acromegaly results from hypersecretion of GH during adulthood. - Photos of a person with gigantism and a person with dwarfism # Hormones of the Anterior Pituitary - Prolactin (PRL) - Stimulates and maintains milk production following childbirth - Function in males is unknown - Adrenocorticotropic hormone (ACTH) - Regulates endocrine activity of the adrenal cortex - Thyroid-stimulating hormone (TSH) - Influences growth and activity of the thyroid gland. # Hormones of the Anterior Pituitary - Gonadotropic hormones - Regulate hormonal activity of the gonads - Follicle-stimulating hormone (FSH) - Stimulates follicle development in ovaries - Stimulates sperm development in testes - Luteinizing hormone (LH) - Triggers ovulation of an egg in females - Stimulates testosterone production in males # Pituitary-Hypothalamus Relationship - Hormonal release is regulated by releasing and inhibiting hormones produced by the hypothalamus. - Hypothalamus produces two hormones: - These hormones are transported to neurosecretory cells of the posterior pituitary: - Oxytocin - Antidiuretic hormone - The posterior pituitary is not strictly an endocrine gland, but does release hormones # Hormones of the Posterior Pituitary - Oxytocin - Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding. - Causes milk ejection in a nursing woman # Hormones of the Posterior Pituitary - Antidiuretic hormone (ADH) - Inhibits urine production by promoting water reabsorption by the kidneys. - In large amounts, causes vasoconstriction leading to increased blood pressure. - Also known as vasopressin - Diagram, showing the posterior pituitary and the hormones it produces, along with their targets. # Thyroid Gland - Found at the base of the throat. - Consists of two lobes and a connecting isthmus. - Produces two hormones: - Thyroid hormone - Calcitonin # Thyroid Gland - Diagram, showing the anatomical location of the thyroid gland. # Thyroid Gland - Thyroid hormone - Major metabolic hormone. - Composed of two active iodine-containing hormones: - Thyroxine (T4) - Triiodothyronine (T3) # Thyroid Gland - Thyroid hormone disorders - Goiters - Thyroid gland enlarges due to lack of iodine - Salt is iodized to prevent goiters - Cretinism - Caused by hyposecretion of thyroxine. - Results in dwarfism during childhood. - Photo of a child with cretinism # Thyroid Gland - Thyroid hormone disorders (continued) - Myxedema - Caused by hypothyroidism in adults - Results in physical and mental sluggishness - Graves disease - Caused by hyperthyroidism - Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos - Close-up photo of a person with Graves' disease # Thyroid Gland - Calcitonin - Decreases blood calcium levels by causing its deposition on bone # Parathyroid Glands - Tiny masses on the posterior of the thyroid. - Secrete parathyroid hormone (PTH) - Stimulate osteoclasts to remove calcium from bone - Stimulate the kidneys and intestine to absorb more calcium. - Raise calcium levels in the blood. # Pancreatic Islets - The pancreas is a mixed gland and has both endocrine (secrete directly into blood) and exocrine (secrete via duct) functions. - The pancreatic islets produce hormones: - Insulin - allows glucose to cross plasma membranes into cells from beta cells. - Glucagon - allows glucose to enter the blood from alpha cells. - These hormones are antagonists that maintain blood sugar homeostasis # Pancreatic Islets - Diagram illustrating the anatomical location of the pancreas and the cells responsible for producing insulin and glucagon. # Pancreatic Islets - Diagram showing a feedback loop involving insulin and glucagon and how they regulate blood glucose levels # Pineal Gland - Found on the third ventricle of the brain - Secretes melatonin - Helps establish the body's wake and sleep cycles - Believed to coordinate the hormones of fertility in humans # Thymus Gland - Located posterior to the sternum - Largest in infants and children - Produces thymosin - Matures some types of white blood cells - Important in developing the immune system # Gonads - Ovaries - Produce two groups of steroid hormone: - Estrogens (Stimulate the development of secondary female characteristics) - Progesterone (Helps in the implantation of an embryo in the uterus; Helps prepare breasts for lactation) - Testes - Produce androgens, such as testosterone (Responsible for adult male secondary sex characteristics; Required for sperm cell production) # Developmental Aspects of the Endocrine System - Most endocrine organs operate smoothly until old age - Menopause is brought about by lack of efficiency of the ovaries. - Problems associated with reduced estrogen are common. - Growth hormone production declines with age. - Many endocrine glands decrease output with age. # Major Endocrine Glands and Hormones | Gland | Hormone | Chemical Class | Representative Actions | Regulated by | |---|---|---|---|---| | Pineal body | Melatonin | Amine | Involved in biological rhythms (daily and seasonal) | Light/dark cycles | | Hypothalamus | _Hormones released by the posterior pituitary_ | | _Releasing and inhibiting hormones that regulate the anterior pituitary (see below)_ | | | Pituitary gland - Posterior lobe | Oxytocin | Peptide | Stimulates contraction of uterus and the milk "let-down" reflex | Nervous system (hypothalamus) in response to uterine stretching and/or suckling of a baby | | Pituitary gland - Posterior lobe | Antidiuretic hormone (ADH) | Peptide | Promotes retention of water by kidneys | Hypothalamus in response to water/salt imbalance | | Pituitary gland - Anterior lobe | Growth hormone (GH) | Protein | Stimulates growth (especially of bones and muscles) and metabolism | Hypothalamic releasing and inhibiting hormones | | Pituitary gland - Anterior lobe | Prolactin (PRL) | Protein | Stimulates milk production | Hypothalamic hormones | | Pituitary gland - Anterior lobe | Follicle-stimulating hormone (FSH) | Protein | Stimulates production of ova and sperm| Hypothalamic hormones | | Pituitary gland - Anterior lobe | Luteinizing hormone (LH) | Protein | Stimulates ovaries and testes | Hypothalamic hormones | | Pituitary gland - Anterior lobe | Thyroid-stimulating hormone (TSH) | Protein | Stimulates thyroid gland | Thyroxine in blood; hypothalamic hormones | | Pituitary gland - Anterior lobe | Adrenocorticotropic hormone (ACTH) | Protein | Stimulates adrenal cortex to secrete glucocorticoids | Glucocorticoids; hypothalamic hormones | | Thyroid gland | Thyroxine (T4) and triiodothyronine (T3) | Amine | Stimulates metabolism | TSH | | Thyroid gland | Calcitonin | Peptide | Reduces blood calcium levels | Calcium level in blood | | Parathyroid glands | Parathyroid hormone (PTH) | Peptide | Raises blood calcium levels | Calcium level in blood | | Thymus gland | Thymosin | Peptide | "Programs" T lymphocytes | Not known | | Adrenal gland - Adrenal medulla | Epinephrine and norepinephrine | Amines | Raise blood glucose level; increase rate of metabolism; constrict certain blood vessels | Nervous system (sympathetic division) | | Adrenal gland - Adrenal cortex | Glucocorticoids | Steroids | Increase blood glucose | ACTH | | Adrenal gland - Adrenal cortex | Mineralocorticoids | Steroids | Promote reabsorption of Na* and excretion of K+ in kidneys | Changes in blood volume or blood pressure; K* (potassium) or Na* levels in blood | | Pancreas | Insulin | Protein | Reduces blood glucose | Glucose level in blood | | Pancreas | Glucagon | Protein | Raises blood glucose | Glucose level in blood| | Gonads - Testes | Androgens | Steroids | Support sperm formation; development and maintenance of male secondary sex characteristics | FSH and LH | | Gonads - Ovaries | Estrogens | Steroids | Stimulate uterine lining growth; development and maintenance of female secondary sex characteristics | FSH and LH | | Gonads - Ovaries | Progesterone | Steroids | Promotes growth of uterine living | FSH and LH |