11 system in our body and their glands and hormones & causes if they don't work properly
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11 organ systems human body glands hormones disorders
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I now have excellent source material from both Costanzo Physiology and Guyton & Hall. Let me compile the full, comprehensive answer covering all 11 body systems.
11 Body Systems: Glands, Hormones & What Happens When They Fail
Here is a complete overview of all 11 organ systems of the human body, with their associated glands, hormones (where applicable), and the consequences of dysfunction.
1. Endocrine System
The endocrine system is the body's hormonal control network. It is the system most directly defined by glands and their secretions.
| Gland | Key Hormones | What Goes Wrong if It Fails |
|---|---|---|
| Hypothalamus | TRH, CRH, GnRH, GHRH, Somatostatin, Dopamine (PIF) | Disrupts all downstream pituitary signals; causes widespread hormonal collapse |
| Anterior Pituitary ("Master Gland") | GH, TSH, ACTH, FSH, LH, Prolactin, MSH | Dwarfism/gigantism (GH), hypothyroidism (TSH), adrenal failure (ACTH), infertility (FSH/LH) |
| Posterior Pituitary | ADH (Vasopressin), Oxytocin | Diabetes insipidus (ADH deficiency - massive water loss); failure of milk ejection/uterine contractions |
| Thyroid | T3 (Triiodothyronine), T4 (Thyroxine), Calcitonin | Hypothyroidism: fatigue, weight gain, cold intolerance, myxedema; Hyperthyroidism: Graves' disease, goitre, heat intolerance, cardiac arrhythmia |
| Parathyroid | PTH (Parathyroid Hormone) | Hypoparathyroidism: hypocalcemia, muscle cramps, tetany; Hyperparathyroidism: kidney stones, bone loss, hypercalcemia |
| Adrenal Cortex | Cortisol (glucocorticoid), Aldosterone (mineralocorticoid), Androgens | Addison's disease (deficiency): fatigue, hypotension, hypoglycemia, hyperpigmentation; Cushing's syndrome (excess): obesity, hypertension, diabetes, osteoporosis |
| Adrenal Medulla | Epinephrine (Adrenaline), Norepinephrine | Pheochromocytoma (tumour causing excess): hypertensive crisis, palpitations, sweating |
| Pancreas (Islets of Langerhans) | Insulin (beta cells), Glucagon (alpha cells), Somatostatin | Insulin deficiency: Type 1 Diabetes; Insulin resistance: Type 2 Diabetes; Glucagonoma: hyperglycemia, weight loss |
| Pineal Gland | Melatonin | Sleep disorders, circadian rhythm disruption |
| Thymus | Thymosin, Thymopoietin | Impaired T-cell maturation, immune deficiency (DiGeorge syndrome if absent) |
| Gonads - Ovaries | Estrogen, Progesterone | Menstrual irregularity, infertility, early menopause, osteoporosis |
| Gonads - Testes | Testosterone | Hypogonadism: low libido, infertility, muscle loss, osteoporosis |
Sources: - Guyton and Hall Textbook of Medical Physiology, Table 75.1 | Costanzo Physiology 7th Ed., Table 9.2
2. Nervous System
Primary structures: Brain, spinal cord, peripheral nerves, sense organs
No classical secretory glands (the hypothalamus bridges endocrine and nervous systems)
Key neurotransmitters (not hormones): Dopamine, Serotonin, Acetylcholine, GABA, Norepinephrine
When it fails:
- Stroke: sudden death of brain tissue from blocked or burst vessels
- Parkinson's disease: loss of dopamine-producing cells - tremor, rigidity, slow movement
- Alzheimer's disease: neurodegeneration - memory loss, cognitive decline
- Multiple Sclerosis: immune destruction of myelin - weakness, vision loss, numbness
- Epilepsy: abnormal electrical discharges - seizures
- Peripheral neuropathy: numbness, pain, weakness in extremities
3. Cardiovascular (Circulatory) System
Primary structures: Heart, blood vessels (arteries, veins, capillaries), blood
Hormones with cardiovascular roles:
- ANP (Atrial Natriuretic Peptide) - secreted by the heart itself - lowers blood pressure by promoting sodium/water excretion
- Aldosterone (from adrenal) acts on kidneys to raise blood pressure
- Epinephrine raises heart rate and force of contraction
When it fails:
- Coronary artery disease: heart attack (myocardial infarction)
- Heart failure: fluid accumulation, breathlessness, reduced exercise tolerance
- Hypertension: increases risk of stroke, kidney damage, heart enlargement
- Arrhythmias: irregular heartbeat - palpitations, syncope, sudden death
- Atherosclerosis: arterial narrowing, reduced blood flow to organs
4. Respiratory System
Primary structures: Lungs, trachea, bronchi, diaphragm, nose
No dedicated hormone-producing glands (lungs produce surfactant - a protein, not a classical hormone)
When it fails:
- Asthma: airway hyperreactivity - wheezing, shortness of breath
- COPD (Chronic Obstructive Pulmonary Disease): permanent airflow obstruction, emphysema
- Pneumonia: infection causing fluid in alveoli, impaired gas exchange
- Pulmonary fibrosis: scarring of lung tissue - progressive breathlessness
- Respiratory failure: dangerously low oxygen or high CO2 - organ failure, death
5. Digestive (Gastrointestinal) System
Primary structures: Mouth, esophagus, stomach, small intestine, large intestine, rectum
Associated glands and hormones:
| Gland/Organ | Hormone/Secretion | Function |
|---|---|---|
| Stomach | Gastrin | Stimulates acid secretion |
| Small intestine (duodenum) | Secretin | Stimulates pancreatic bicarbonate secretion |
| Small intestine | CCK (Cholecystokinin) | Stimulates bile release and pancreatic enzymes |
| Small intestine | GIP (Gastric Inhibitory Peptide) | Inhibits acid, stimulates insulin |
| Pancreas (exocrine) | Amylase, Lipase, Proteases | Digest carbohydrates, fats, proteins |
| Liver | Bile (not a hormone) | Emulsifies fats |
| Salivary glands | Salivary amylase | Begins carbohydrate digestion |
When it fails:
- Peptic ulcers: H. pylori or NSAID-related erosion of stomach lining
- Crohn's disease / Ulcerative colitis: chronic inflammation - pain, diarrhoea, malnutrition
- Liver failure: jaundice, coagulopathy, encephalopathy
- Pancreatitis: severe abdominal pain, fat malabsorption
- Colorectal cancer: altered bowel habits, bleeding, obstruction
6. Urinary (Renal) System
Primary structures: Kidneys, ureters, bladder, urethra
Hormones produced by or acting on kidneys:
| Source | Hormone | Action |
|---|---|---|
| Kidneys | Erythropoietin (EPO) | Stimulates red blood cell production |
| Kidneys | Renin | Activates renin-angiotensin system to raise blood pressure |
| Kidneys | Calcitriol (active Vitamin D) | Increases calcium absorption from gut |
| Adrenal (acts on kidney) | Aldosterone | Promotes Na+ reabsorption, K+ excretion |
| Posterior pituitary (acts on kidney) | ADH | Promotes water reabsorption |
When it fails:
- Acute kidney injury: rapid loss of filtration - fluid overload, electrolyte disturbances
- Chronic kidney disease: hypertension, anaemia (low EPO), bone disease (low Vit D), uraemia
- Nephrotic syndrome: massive proteinuria, oedema, hyperlipidaemia
- Kidney stones: severe flank pain, obstruction, infection
- Urinary tract infection (UTI): dysuria, frequency, risk of pyelonephritis
7. Muscular System
Primary structures: Skeletal muscles, smooth muscles, cardiac muscle
No dedicated glands, but responds to:
- Testosterone and Growth Hormone: promote muscle growth (anabolic effects)
- Cortisol: causes muscle breakdown (catabolic effect at excess)
- Insulin: promotes glucose uptake into muscle
When it fails:
- Muscular dystrophy (e.g., Duchenne): progressive muscle weakness and wasting
- Myasthenia gravis: autoimmune blockade of acetylcholine receptors - fatigue, weakness
- Rhabdomyolysis: muscle breakdown - releases myoglobin, can cause kidney failure
- Sarcopenia: age-related muscle loss
- Fibromyalgia: widespread muscle pain and fatigue
8. Skeletal System
Primary structures: 206 bones, cartilage, joints, ligaments
Hormonal regulation of bone:
| Hormone | Source | Effect on Bone |
|---|---|---|
| PTH | Parathyroid | Increases bone resorption (raises blood Ca2+) |
| Calcitonin | Thyroid C-cells | Decreases bone resorption (lowers blood Ca2+) |
| Calcitriol (Vit D) | Kidneys | Promotes calcium absorption and bone mineralisation |
| Estrogen | Ovaries | Protects against bone loss |
| GH / IGF-1 | Pituitary / Liver | Promotes bone growth and lengthening |
When it fails:
- Osteoporosis: low bone density - fracture risk (hip, spine, wrist)
- Osteomalacia / Rickets: poor mineralisation from Vitamin D deficiency
- Paget's disease: disorganised bone remodelling - pain, deformity
- Osteoarthritis: cartilage destruction - joint pain and stiffness
- Fractures: from trauma or underlying bone disease
9. Integumentary System
Primary structures: Skin, hair, nails, sweat glands, sebaceous glands
Associated glands:
| Gland | Secretion | Function |
|---|---|---|
| Sweat glands (eccrine) | Sweat | Thermoregulation, excretion of waste |
| Sebaceous glands | Sebum (oil) | Lubricates and waterproofs skin/hair |
| Hair follicles | Hair | Protection, sensation |
| Skin | Vitamin D3 (precursor) | Converted to active Vitamin D in kidneys |
When it fails:
- Eczema (Atopic Dermatitis): immune-driven skin inflammation, intense itching
- Psoriasis: rapid skin cell turnover - plaques, scaling
- Acne: excess sebum + bacterial overgrowth in follicles (often androgen-driven)
- Melanoma / Skin cancer: UV-induced DNA mutation in melanocytes
- Burns: loss of barrier function - infection, fluid loss, hypothermia
10. Immune (Lymphatic) System
Primary structures: Lymph nodes, spleen, thymus, bone marrow, tonsils, white blood cells
Associated gland and hormone:
| Gland | Hormone | Function |
|---|---|---|
| Thymus | Thymosin, Thymulin | Matures T-lymphocytes; critical in childhood |
| Bone marrow | (produces cytokines) | Source of all blood and immune cells |
When it fails:
- HIV/AIDS: destruction of CD4+ T-cells - susceptibility to opportunistic infections
- Lupus (SLE): autoimmune attack on multiple organs - joints, kidneys, skin, brain
- Rheumatoid arthritis: autoimmune joint destruction
- Lymphoma / Leukaemia: malignant proliferation of immune/blood cells
- Primary immunodeficiency (e.g., SCID): recurrent severe infections from birth
11. Reproductive System
Primary structures (Male): Testes, epididymis, vas deferens, prostate, penis
Primary structures (Female): Ovaries, fallopian tubes, uterus, cervix, vagina
Glands and hormones:
| Gland | Hormones | Functions |
|---|---|---|
| Testes | Testosterone, Inhibin | Sperm production, male secondary sex characteristics |
| Ovaries | Estrogen, Progesterone, Inhibin | Ovulation, menstrual cycle, pregnancy maintenance |
| Placenta (during pregnancy) | hCG, Progesterone, Estrogen, HPL | Maintains pregnancy, prepares breasts for lactation |
| Prostate (Male) | PSA (marker, not a hormone) | Contributes to seminal fluid |
When it fails:
- Polycystic Ovary Syndrome (PCOS): excess androgens - irregular periods, infertility, hirsutism
- Endometriosis: ectopic uterine tissue - chronic pelvic pain, infertility
- Male hypogonadism: low testosterone - infertility, erectile dysfunction, osteoporosis
- Ovarian/Testicular cancer: malignant growths disrupting hormone and gamete production
- Premature ovarian failure / Early menopause: estrogen deficiency - hot flushes, bone loss
Quick Reference Summary
| # | System | Key Gland(s) | Major Hormones | Main Disorder if Fails |
|---|---|---|---|---|
| 1 | Endocrine | All glands listed above | T3/T4, Insulin, Cortisol, etc. | Diabetes, Thyroid disorders, Addison's |
| 2 | Nervous | Hypothalamus | CRH, TRH, GnRH | Parkinson's, Alzheimer's, Epilepsy |
| 3 | Cardiovascular | Heart (ANP) | ANP, Epinephrine | Heart attack, Heart failure, Stroke |
| 4 | Respiratory | None | Surfactant | Asthma, COPD, Respiratory failure |
| 5 | Digestive | Pancreas, Stomach, Intestine | Gastrin, CCK, Secretin | Ulcers, IBD, Liver failure |
| 6 | Urinary | Kidneys | EPO, Renin, Calcitriol | CKD, Kidney stones, UTI |
| 7 | Muscular | None | Testosterone, GH (act on it) | Muscular dystrophy, Myasthenia gravis |
| 8 | Skeletal | None | PTH, Calcitonin, Estrogen (act on it) | Osteoporosis, Rickets, Fractures |
| 9 | Integumentary | Sweat & Sebaceous glands | Sebum, Vit D3 precursor | Eczema, Melanoma, Acne |
| 10 | Immune/Lymphatic | Thymus, Bone marrow | Thymosin | HIV/AIDS, Lupus, Lymphoma |
| 11 | Reproductive | Testes, Ovaries, Placenta | Testosterone, Estrogen, Progesterone | PCOS, Infertility, Hypogonadism |
Sources:
- Guyton and Hall Textbook of Medical Physiology, Table 75.1 - Endocrine Glands, Hormones, and Their Functions
- Costanzo Physiology 7th Edition, Table 9.2 - Summary of Endocrine Glands and Actions of Hormones
- Verywell Health - Organ Systems
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