Endocrine and Lymphatic Systems PDF

**ENDOCRINE SYSTEM** The Endocrine (or Hormonal) System - Hormones Australia The endocrine system consists of glands and tissues that secrete hormones. Hormones - Chemical signals that affect the activity of other glands or tissues. - Reproduction - Growth and development - Immune...

**ENDOCRINE SYSTEM** The Endocrine (or Hormonal) System - Hormones Australia The endocrine system consists of glands and tissues that secrete hormones. Hormones - Chemical signals that affect the activity of other glands or tissues. - Reproduction - Growth and development - Immune system response - Homeostasis **Flow of Nerve Impulse** 1. Nerve impulse arrives at the synaptic end bulb of the pre-synaptic axon. 2. Voltage-gated Ca^2^ channels open during depolarization. 3. Ca^2^ influx triggers exocytosis of synaptic vesicles, releasing neurotransmitters into the synaptic cleft. 4. Neurotransmitters bind to post-synaptic receptors, opening ligand-gated channels. 5. Ions flow through channels, leading to a change in membrane voltage (post-synaptic potential) 6. Post-synaptic potential can be: depolarization or hyperpolarization - Depolarization -- excitation - Hyperpolarization -- inhibition 7. Depolarization reaching threshold triggers an action potential in the post-synaptic neuron's axon. **Comparison of Control by the Nervous and Endocrine System** **Characteristic** **Nervous System** **Endocrine System** ------------------------- ------------------------------------------------------------------------------------- ------------------------------------------------------------- Mediator Molecules Neurotransmitters released locally in response to nerve impulses. Hormones delivered to tissues throughout the body by blood. Site of mediator action Close to site of release, at synapse, binds to receptors in post-synaptic membrane. Far from site of release. Types of target cells Muscle (smooth, cardiac, skeletal) cells, gland cells, other neurons. Cells throughout the body. Time to onset of action Within milliseconds (thousands of a second). Seconds to hours or days. Duration of action Generally briefer (milliseconds). Generally longer (seconds to days). **Exocrine Glands** - Secretes non-hormonal chemicals into ducts which transport chemicals to a specific location. - Includes: - Sudoriferous (sweat) - Sebaceous (oil) - Mucous - Digestive glands - Salivary glands **Endocrine Glands** - Ductless glands located throughout the body. - Secretes hormones directly into the bloodstream. **Functions of Hormones** 1. Chemical composition and volume of internal environment (interstitial fluid). 2. Metabolism and energy balance. 3. Contraction of smooth and cardiac muscle fibers. 4. Glandular secretions. 5. Some immune system activities. 6. Control growth and development. 7. Regulate operation of reproductive systems. 8. Help establish circadian rhythms. +-----------------------------------+-----------------------------------+ | **Circulating Hormones** | **Local Hormones** | +===================================+===================================+ | - Acts on distant targets. | - Paracrine act on neighboring | | | cells. | | - Travels through the blood. | | +-----------------------------------+-----------------------------------+ **Classes of Hormones** 1. Lipid-soluble hormones 2. Steroid hormones 3. Thyroid hormones (T3, T4) 4. Nitric Oxide 5. Water-soluble hormones 6. Amine hormones 7. Peptide hormones and protein hormones 8. Eicosanoid hormones Hormone Entry - Lipid-soluble hormones move from the blood through the cell membrane into the cell. Receptor Activation - If the cell is a target, the hormone binds to receptors in the cytosol or nucleus. - Activated receptors influence gene expression, turning specific genes on or off. Gene Expression and mRNA - Transcription of DNA occurs, creating mRNA. - mRNA exits the nucleus and guides protein synthesis on ribosomes. - Newly formed proteins modify cell activity, leading to hormone-specific responses. **Summary of Endocrine Glands and Hormones** +-----------------------+-----------------------+-----------------------+ | **Glands** | **Hormones** | **Effect of | | | | Hormones** | +=======================+=======================+=======================+ | Pineal Gland | Melatonin | Affects reproductive | | | | development and daily | | | | physiologic cycles. | +-----------------------+-----------------------+-----------------------+ | Pituitary Gland | Growth hormone | Controls growth of | | | | bones and muscles. | +-----------------------+-----------------------+-----------------------+ | | Anti-diuretic hormone | Increases | | | | reabsorption of water | | | | in kidneys. | +-----------------------+-----------------------+-----------------------+ | | Gonadotrophins | Controls development | | | | of ovaries and | | | | testes. | +-----------------------+-----------------------+-----------------------+ | Thyroid Gland | Thyroxine | Controls rate of | | | | metabolism and rate | | | | that glucose is used | | | | up in respiration and | | | | promote growth. | +-----------------------+-----------------------+-----------------------+ | Adrenal Gland | Adrenaline | Prepares body for | | | | emergencies. | | | | | | | | Increases heart rate | | | | along with rate and | | | | depth of breathing, | | | | raises blood sugar | | | | level to make glucose | | | | more available for | | | | respiration. | | | | | | | | Diverts blood from | | | | gut to limbs. | +-----------------------+-----------------------+-----------------------+ | Pancreas | Insulin | Converts excess | | | | glucose to glycogen | | | | (liver). | +-----------------------+-----------------------+-----------------------+ | | Glucagon | Converts glycogen | | | | back to glucose | | | | (liver). | +-----------------------+-----------------------+-----------------------+ | Ovaries | Estrogen | Controls ovulation | | | | and secondary sexual | | | | characteristics. | +-----------------------+-----------------------+-----------------------+ | | Progesterone | Prepares uterus | | | | lining for receiving | | | | an embryo. | +-----------------------+-----------------------+-----------------------+ | Testes | Testosterone | Controls sperm | | | | production and | | | | secondary sexual | | | | characteristics. | +-----------------------+-----------------------+-----------------------+ | Thymus | Thymosin | Promotes production | | | | and maturation of | | | | WBCs. | +-----------------------+-----------------------+-----------------------+ **HYPOTHALAMUS** - Located beneath the thalamus in the brain. - Considered the "master switchboard" of the endocrine system. - Signals the pituitary gland. - Controls the glandular secretions of the pituitary gland. - Regulates the internal environment through the autonomic system. - Heartbeat - Water balance - Body temperature **PITUITARY GLAND** - Major hormone producer. - Small gland, about 1cm in diameter. - Connected to the hypothalamus by a stalk-like structure. - Has 2 portions: - Anterior pituitary - Posterior pituitary Anterior Pituitary - Controlled by hypothalamus through hypothalamic releasing hormone and inhibiting hormone. - Releases 6 types of hormones: - Thyroid Stimulating Hormone (TSH) - Adrenocorticotropic Hormone (ACTH) - Gonadotropic Hormone (FSH & LH) - Prolactin (PRL) - Melanocyte Stimulating Hormone (MSH) - Growth Hormone (GH) Posterior Pituitary stores 2 hormones: Vasopressin or Antidiuretic Hormone - Causes kidneys to form concentrated urine and conserve water. Oxytocin - Stimulates uterine contraction during labor and causes the release of milk. *\*Hypocalcemia* - Increased susceptibility to epilepsy (difficulty controlling muscle movements). - Manifestations: muscle cramps and muscle spasms. **THYROID GLAND** - Located in the neck, just below the larynx. - Produces: - Triiodothyronine (T3) - Thyroxine (T4) - Calcitonin T3 and T4 - Stimulates and maintains metabolic rate, normal heart rate, blood pressure, and body temperature. - More glucose breakdown over fat usage for energy. - Requires iodin for hormonal production. \*Simple Goiter -- Iodin deficient Cretinism -- thyroid fails to develop Grave's disease -- oversecretion of thyroid hormone Cretinism - A condition characterized by severely stunted physical and mental growth. - Caused by congenital hypothyroidism or the untreated congenital deficiency of thyroid hormones. - Results in significant developmental delays. Grave's Disease - Immune system disorder leading to the overproduction of thyroid hormones (hyperthyroidism). Calcium plays an important role in nervous conduction, muscle contraction, and blood clotting. Calcitonin - Maintains calcium levels in the blood and inhibits calcium release from the bone. - Temporarily reduces the activity and number of osteoclasts. - Blood Ca lowers, calcitonin inhibited. - Low Ca levels stimulate parathyroid hormones. Action of Thyroid Hormone - Increases basal metabolic rate. - Regulates the development and growth of nervous tissue and bones. - Enhance some actions of catecholamines. - Stimulate lipolysis. - Stimulate protein synthesis. - Increase body temperature (calorigenic effect) - Stimulate the synthesis of Na^+^, K^+^ ATPase - Increase the use of glucose and fatty acids for ATP production. Parathyroid Hormone - Attached to or embedded in the back surface of the thyroid gland, 2 in each lobe. - Regulates Ca level in the blood. - By increasing reabsorption of Ca in the kidneys and increasing Ca uptake from the digestive system. - Important in promoting proper nerve and muscle function and maintaining bone structure. - Loss of PTH results in violent muscular spasms known as TETANY. Action of Parathyroid Hormones - Slows rate at which Ca^2^ and Mg^2^ are lost from blood into the urine. - Increases the loss of HPO~4~ from blood into the urine. - Formation of calcitrol. **Disorders of the Thyroid Gland** +-----------------------------------+-----------------------------------+ | **Hypothyroidism** | **Hyperthyroidism** | +===================================+===================================+ | - Intolerance to cold. | - Intolerance to heat | | | | | - Thick tongue | - Bluging eyes | | | | | - Irregularities w/ | - Enlarged thyroid | | menstruation | | | | - Tachycardia | | - Bradycardia | | +-----------------------------------+-----------------------------------+ **ADRENAL GLANDS** - Two adrenal glands sit atop the kidneys. - Each adrenal gland consists of: - Outer -- adrenal cortex - Inner -- adrenal medulla - Controlled by hypothalamus. - Where it simulates anterior pituitary to release ACTH. - ACTH reacts at the adrenal cortex. Adrenal Cortex - Outer portion. - Makes up 80% of the mass of the gland. +-----------------------------------+-----------------------------------+ | Glucocorticoid | - Also known as Cortisol. | | | | | | - Affects CHO, protein and fat | | | metabolism, and helps cope | | | with stress. | +===================================+===================================+ | Mineralocorticoid | - Also known as Aldosterone. | | | | | | - Regulates sodium reabsorption | | | and potassium excretion by | | | the kidneys. | | | | | | - Affects water and salt | | | balance. | +-----------------------------------+-----------------------------------+ | Androgens | - Sex drive | +-----------------------------------+-----------------------------------+ | Dehydroepiandrosterone (DHEA) | | +-----------------------------------+-----------------------------------+ | Testosterone | | +-----------------------------------+-----------------------------------+ | Estrogen | | +-----------------------------------+-----------------------------------+ \*Addisons Disease -- decreased activity of the adrenal cortex. Cushing's Syndrome -- increased adrenal cortex activity. Adrenal Medulla - Inner portion specialized part of sympathetic nervous system. - Secretes adrenaline and noradrenaline "fight or flight" hormones. - Nerve impulses from sympathetic system causes hormone secretion. +-----------------------------------+-----------------------------------+ | Epinephrine (Adrenaline) | Norepinephrine (Noradrenaline) | +===================================+===================================+ | - Increases heart rate, BP, | - Stimulates heart muscles by | | glycogen to glucose, and | increasing the rate and | | increases metabolic rate. | strength of the heartbeat. | +-----------------------------------+-----------------------------------+ Addison's Disease - Inadequate production of cortisol and aldosterone. - Primary adrenal insufficiency. Secondary Adrenal Insufficiency - Insufficient release of ACTH by the pituitary gland. Cushing's Syndrome - Hypercortisolism. **Reproductive Glands** Gonads -- produces gametes and a group of sex hormones. - Sex hormones regulate body changes that begin with puberty. FSH & LH -- stimulates secretion of sex hormones from gonads. Ovaries -- produces estrogen and progesterone. Testes -- produces testosterone. **PANCREAS** - Both an exocrine (duct) and an endocrine gland. - Hormone-producing cells -- Islets of Langerhans. Alpha Cells Secretes glucagon ------------- ---------------------------------------------------------------------------------------- Beta Cells Secretes insulin Delta Cells Secretes somatostatin F Cells Secretes pancreatic polypeptide Insulin Stimulates target cells to take up glucose for use or storage, reducing blood glucose. Glucagon Breaks down stored glycogen, increasing glucose levels. Hypoglycemia - Caused by excess insulin or low blood sugar. - Causes the release of glucagon and epinephrine. - Symptoms: lethargy, dizziness, nervousness, overactivity, and unconsciousness and death. Hyperglycemia - Caused by low insulin or high blood sugar. - Causes nausea, rapid breathing, oxygen deficiency, circulatory and nervous failure, diabetic coma or death. **Type I vs Type II Diabetes** Type I - Genetic - Insulin -- dependent - Juvenile onset - Little or no insulin - Requires strict diet and daily insulin injection. Type II - Acquired - Insulin resistant - Non -- insulin dependent - Adult onset - Producing normal or reduced amounts of insulin - Cells are unable to respond due to lack of insulin receptors. **Feature** **Type I** **Type II** -------------------------------- ----------------- --------------------------------- Onset Sudden Gradual Age at onset Any age Mostly adults Body habitus Thin or normal Often obese Ketoacidosis Common Rare Autoantibodies Usually present Absent Endogenous Insulin Low or absent Normal, decreased, or increased Concordance in identical twins 50% 90 -- 95% Prevalence Less prevalent More prevalent **THYMUS GLAND** - Located beneath the sternum (breastbone) and between the lungs. - Consists mostly of T-cells. - Plays an important role in the immune system. - Secretes thymosin. - Stimulates the formation of T-cells and help defend the body from pathogens. **PINEAL GLAND** - Located near the base of the brain. - Secretes melatonin - Regulates daily sleep-wake cycle. - Circadian rhythms -- controlled biological clock located in the hypothalamus. **LYMPHATIC SYSTEM** - Contributes to homeostasis by draining interstitial fluid, as well as providing mechanisms for defenses against disease. - System of vessels, cells, and organs that carries excess fluids to the bloodstream and filters pathogens from the blood. **Functions of the Lymphatic System** 1. Drain excess interstitial fluid -- lymphatic vessels drain excess interstitial fluid from tissue spaces and return it to the blood. 2. Transports dietary lipids -- lipids and lipid-soluble vitamins (A,D,E,K) are absorbed by the gastrointestinal tract. 3. Carries out immune responses -- initiates highly specific responses directed against particular microbes or abnormal cells. **Definition of Terms** +-----------------------------------+-----------------------------------+ | Lymph | - Fluid circulating. | | | | | | - Fluid that contains WBCs that | | | defend against | | | microorganisms. | | | | | | - Normal color: clear or pale | | | yellow | +===================================+===================================+ | Lymph Vessels | - Vessels that carry lymph | | | throughout the body. | +-----------------------------------+-----------------------------------+ | Lymph Nodes | - Glands found throughout the | | | lymph vessels. | | | | | | - Along with the spleen, it is | | | where WBCs fight infection. | +-----------------------------------+-----------------------------------+ \*Spleen -- considered as a filtering station: filters lymph before it enters the blood stream by filtering impurities and harmful microorganisms. **Lymphatic Flow Mechanisms** Skeletal Muscle Pump - Skeletal muscle contractions compress lymphatic vessels and veins, helping move lymph. Milking Action - Contractions create a "milking action", pushing lymph toward the junction of the internal jugular and subclavian veins. Respiratory Pump - Inhalation creates pressure changes that facilitate lymph flow: - Lymph moves from the abdominal area (higher pressure) to the thoracic area (low pressure). - During exhalation, valves prevent backflow of lymph as pressures reverse. **Lymph Capillaries** - Have greater permeability. - Can absorb larger molecules such as proteins and lipids. **Fat Absorption in the Small Intestines** - Fatty acids and monoglycerides aggregate and emulsify, resulting in micelles. - Micelles + golgi apparatus = chylomicrons - Lymph in the lacteal transports chylomicrons away from the intestines. **Lymphatic Ducts** - Also known as large ducts. - Formed when lymph vessels join together. - Consists of: - Thoracic duct - Right lymphatic duct **Thoracic Duct** - Size: approximately 40 cm. - Crucial component of the lymphatic system, responsible for draining lymph from various regions of the body. - Situated in front of the bodies of the first 2 lumbar vertebrae. - Acts as the starting point of the thoracic duct. Drainage Areas Lymphatic Fluid from: - Both legs - Pelvic and abdominal cavities - Left side of thorax - Head and neck - Left arm **Right Lymphatic Duct** - Approximately 1cm long. - Empties at the junction of right internal jugular and right subclavian veins. - Areas drained: - Neck - Head - Thorax - Right arm **LYMPH NODES** - Oval or bean-shaped. - Consists of B and T-cells. - Lymph passes through a series of nodes, usually 8 -- 10, as it circulates through the body before re-entering the bloodstream. - Exhibit a wide range in size, with some as small as a pinhead, and the largest approximately the size of an almond. **Structures of Lymph Nodes** Trabeculae Outer capsule of fibrous tissue that dips down into the node substance, forming partitions. ------------------------------ --------------------------------------------------------------------------------------------- Reticular & Lymphatic Tissue Contain many lymphocytes and macrophages; essential components of the immune system. Afferent Lymph Vessels Where lymph enters lymph nodes, carrying pathogens and antigens. Efferent Lymph Vessels Where processed lymph exits. Hilum Concave surface where blood vessels and nerves exit Lymph Nodes are arranged in deep and superficial groups - Cervical nodes - Axillary nodes - Pelvic nodes - Abdominal nodes - Inguinal nodes **Larger Lymphatic Vessels** - Trunks - Tiny capillaries join up to form larger lymph vessels. - The walls of lymph vessels are about the same thickness as small veins and have the same layers of tissue: - Tunica Adventitia -- consists of a fibrous layer that provides structural support. - Tunica Media -- contains elastin and smooth muscular tissue for vessel flexibility and contraction. - Tunica Intima -- comprised of endothelium, forming the innermost layer and promoting the smooth flow of lymph. **Sequence of Fluid Flow** 1. Blood capillaries (blood) 2. Interstitial spaces (interstitial fluid) 3. Lymphatic capillaries (lymph) 4. Lymphatic vessels (lymph) 5. Lymphatic ducts (lymph) 6. Junction of the internal jugular vein and subclavian veins (blood) **Lymphatic System and Lymph Drainage** Formation of Lymph Trunks - Lymphatic vessels exiting lymph nodes unite to form lymph trunks. - Principal trunks include: lumbar trunks, intestinal trunk, bronchomediastinal trunk, subclavian trunk, and jugular trunks. Lumbar trunks Drain lymph from lower limbs, pelvic wall, kidneys, adrenal glands, and abdominal wall. -------------------------- ----------------------------------------------------------------------------------------- Intestinal trunk Drains lymph from stomach, intestines, pancreas, spleen, and part of the liver. Bronchomediastinal trunk Drains lymph from thoracic wall, lungs, and heart. Subclavian trunk Drains lymph from the upper limbs. Jugular trunks Drains lymph from the head and neck. Main Lymph Channels - Largest lymph vessels. - Lymph passes from lymph trunks into 2 primary channels: thoracic duct and cisterna chyli. +-----------------------------------+-----------------------------------+ | Thoracic duct | Main duct for lymph returns to | | | the bloodstream. | | | | | | Receives lymph from the left | | | jugular vein, left subclavian, | | | left bronchomediastinal trunks. | +===================================+===================================+ | Cisterna chyli | Receives lymph from the right and | | | left lumbar trunks and from the | | | intestinal trunk. | +-----------------------------------+-----------------------------------+ \*Right Lymphatic Duct -- drainks into venous blood. Spleen Structure - Oval in shape with the hilum on the lower medial border. - Anterior surface is covered with peritoneum. Trabeculae Fibroelastic capsule that dips into the organ. -------------- -------------------------------------------------------------------------------------------------------------------- Splenic pulp Cellular material consisting of lymphocytes and macrophages. Red pulp Part suffused with blood. White pulp Consists of areas of lymphatic tissue where there are sleeves of lymphocytes and macrophages around blood vessels. **IMMUNITY** - Lymphocytes are primary cells of adaptive immune responses. - B-cells and T-cells: basic types of lymphocytes. - B-cells mature in the red bone marrow. - T-cells mature in the thymus. - Both initially develop from the bone marrow. - T-cells migrate from bone marrow to the thymus gland where they further mature. - B-cells and T-cells are circulating in the bloodstream and lymph. - Residing in secondary lymphoid organs including the spleen and lymph nodes. *\*Spleen -- filters damaged RBCs or senescent cells. Serves as a graveyard of blood cells.* *Littoral cells -- macrophages in the spleen.*