2.4 Musculoskeletal, Urinary & Reproductive Systems
Key Takeaways
- The adult skeleton has 206 bones divided into the axial skeleton (skull, spine, ribcage) and appendicular skeleton (limbs, shoulders, pelvis)
- The three types of muscle tissue are skeletal (voluntary), smooth (involuntary, organ walls), and cardiac (involuntary, heart only)
- The kidneys filter blood, producing approximately 1-2 liters of urine daily; the nephron is the functional unit of the kidney
- Normal urine output is 30-50 mL/hour in adults; oliguria (<400 mL/day) and anuria (<100 mL/day) indicate kidney dysfunction
- The female reproductive cycle averages 28 days with four phases: menstrual, follicular, ovulation, and luteal
- Common musculoskeletal conditions include osteoarthritis, osteoporosis, rheumatoid arthritis, fractures, and sprains/strains
Last updated: March 2026
Musculoskeletal, Urinary & Reproductive Systems
Musculoskeletal System
Skeletal System:
- 206 bones in the adult skeleton
- Functions: Support, protection, movement, mineral storage (calcium, phosphorus), blood cell production (hematopoiesis in red bone marrow)
| Division | Components | Examples |
|---|---|---|
| Axial skeleton (80 bones) | Skull, vertebral column, rib cage, hyoid | Cranium, mandible, cervical/thoracic/lumbar vertebrae, sternum |
| Appendicular skeleton (126 bones) | Upper limbs, lower limbs, shoulder girdle, pelvic girdle | Humerus, radius, ulna, femur, tibia, fibula, scapula, clavicle |
Vertebral Column:
- Cervical (C1-C7) — Neck region; C1 is atlas, C2 is axis
- Thoracic (T1-T12) — Upper back; attach to ribs
- Lumbar (L1-L5) — Lower back; largest vertebrae
- Sacrum (S1-S5 fused) — Posterior pelvis
- Coccyx (3-4 fused) — Tailbone
Joint Types:
| Type | Movement | Examples |
|---|---|---|
| Synovial | Freely movable | Knee, shoulder, hip, elbow |
| Cartilaginous | Slightly movable | Vertebral discs, pubic symphysis |
| Fibrous | Immovable | Skull sutures |
Common Musculoskeletal Conditions:
- Osteoarthritis — Degenerative joint disease; wear and tear of cartilage
- Rheumatoid arthritis — Autoimmune; systemic joint inflammation
- Osteoporosis — Decreased bone density; increased fracture risk
- Fracture — Bone break (closed/simple vs. open/compound)
- Sprain — Ligament injury (connects bone to bone)
- Strain — Muscle or tendon injury (connects muscle to bone)
- Herniated disc — Disc material pressing on spinal nerves
- Carpal tunnel syndrome — Compression of median nerve in the wrist
Urinary System
| Structure | Function |
|---|---|
| Kidneys (2) | Filter blood, produce urine, regulate fluid/electrolyte balance, acid-base balance, blood pressure (renin), red blood cell production (erythropoietin) |
| Ureters (2) | Transport urine from kidneys to bladder via peristalsis |
| Bladder (1) | Stores urine (capacity ~500 mL) |
| Urethra (1) | Transports urine from bladder to outside the body |
The Nephron (functional unit of the kidney): Each kidney contains about 1 million nephrons that filter blood and produce urine:
- Glomerulus — Capillary network that filters blood
- Bowman's capsule — Collects the filtrate
- Proximal convoluted tubule — Reabsorbs glucose, amino acids, sodium, water
- Loop of Henle — Concentrates urine; reabsorbs water and sodium
- Distal convoluted tubule — Fine-tunes electrolyte balance
- Collecting duct — Collects final urine; influenced by ADH
Urine Output:
| Term | Definition |
|---|---|
| Normal output | 30-50 mL/hour (1,000-2,000 mL/day) |
| Polyuria | Excessive urine output (>2,500 mL/day) |
| Oliguria | Decreased urine output (<400 mL/day) |
| Anuria | Absent urine output (<100 mL/day) |
| Hematuria | Blood in the urine |
| Proteinuria | Protein in the urine |
| Glycosuria | Glucose in the urine |
Common Urinary Conditions:
- UTI — Urinary tract infection; most common in females; burning urination, frequency
- Kidney stones (nephrolithiasis) — Mineral deposits; severe flank pain
- Chronic kidney disease — Progressive loss of kidney function
- Incontinence — Involuntary loss of urine (stress, urge, overflow types)
Reproductive System
Male Reproductive System:
| Structure | Function |
|---|---|
| Testes | Produce sperm and testosterone |
| Epididymis | Sperm maturation and storage |
| Vas deferens | Transports sperm from epididymis |
| Seminal vesicles | Produce fructose-rich fluid (60% of semen) |
| Prostate gland | Produces alkaline fluid to protect sperm |
| Urethra | Passageway for semen and urine (not simultaneously) |
| Penis | Delivers sperm; urination |
Female Reproductive System:
| Structure | Function |
|---|---|
| Ovaries | Produce eggs (ova), estrogen, and progesterone |
| Fallopian tubes | Transport eggs from ovary to uterus; fertilization site |
| Uterus | Site of embryo implantation and fetal development |
| Cervix | Lower portion of uterus; opening to vagina |
| Vagina | Birth canal; receives sperm |
Menstrual Cycle (~28 days):
| Phase | Days | Events |
|---|---|---|
| Menstrual | 1-5 | Uterine lining sheds; bleeding occurs |
| Follicular | 1-13 | Follicle matures in ovary; estrogen rises; endometrium thickens |
| Ovulation | Day 14 | Mature egg released from ovary; LH surge triggers ovulation |
| Luteal | 15-28 | Corpus luteum produces progesterone; endometrium maintained; if no fertilization, progesterone drops and menstruation begins |
Common Reproductive Conditions:
- Benign prostatic hyperplasia (BPH) — Enlarged prostate; urinary difficulty in older males
- Prostate cancer — Most common cancer in males; PSA screening
- Endometriosis — Uterine tissue grows outside the uterus; painful periods
- Polycystic ovary syndrome (PCOS) — Hormonal imbalance; irregular periods, ovarian cysts
- Cervical cancer — Often caused by HPV; detected by Pap smear screening
- Sexually transmitted infections — Chlamydia, gonorrhea, syphilis, HIV, herpes, HPV
Lymphatic/Immune System
The lymphatic system works closely with the cardiovascular system and plays a crucial role in immunity:
| Component | Function |
|---|---|
| Lymph nodes | Filter lymph fluid; trap pathogens; contain lymphocytes |
| Spleen | Filters blood; removes old RBCs; stores blood; produces lymphocytes |
| Thymus | T-cell maturation (most active in childhood) |
| Tonsils | Trap pathogens entering through mouth/nose |
| Bone marrow | Produces all blood cells including lymphocytes |
Immunity Types:
- Innate (natural) immunity — Non-specific; present at birth (skin, mucous membranes, inflammation, fever)
- Adaptive (acquired) immunity — Specific; develops after exposure to pathogens or vaccination
- Active immunity — Body makes its own antibodies (infection or vaccination)
- Passive immunity — Receiving antibodies from another source (maternal antibodies, immunoglobulin injections)
Test Your Knowledge
Which of the following correctly describes the difference between a sprain and a strain?
A
B
C
D
Test Your Knowledge
The functional unit of the kidney responsible for filtering blood and producing urine is the:
A
B
C
D
Test Your Knowledge
On approximately what day of the menstrual cycle does ovulation typically occur?
A
B
C
D
Test Your Knowledge
Active immunity is developed when:
A
B
C
D
Test Your Knowledge
Oliguria is defined as:
A
B
C
D