🔬 New Lesson 19
Anatomy, Physiology & Pathophysiology
How body systems work, what goes wrong in disease, and the why behind every nursing action.
Body Systems Overview
Key Body Systems — What Goes Wrong in Disease
| System | Normal Function | Common Disease Process |
|---|---|---|
| Cardiovascular | Pumps blood, delivers O2 | Heart failure, MI, hypertension, dysrhythmias |
| Respiratory | Gas exchange, O2/CO2 | COPD, asthma, pneumonia, PE |
| Renal/Urinary | Filter blood, regulate fluid/electrolytes | AKI, CKD, UTI, nephrolithiasis |
| Endocrine | Hormone regulation of metabolism | DM, thyroid disorders, adrenal disorders |
| Neurological | Control, communication, sensation | Stroke, seizures, increased ICP |
| GI/Hepatic | Digestion, absorption, detoxification | PUD, cirrhosis, pancreatitis, IBD |
| Immune/Lymphatic | Defense against pathogens | HIV/AIDS, allergies, autoimmune disorders |
| Musculoskeletal | Structure, movement, protection | Fractures, arthritis, osteoporosis |
Homeostasis
Homeostasis — The Body's Balance
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Homeostasis is the body's ability to maintain a stable internal environment despite changes. Disease occurs when homeostatic mechanisms are overwhelmed or fail.
| Parameter | Normal Range | Regulatory System |
|---|---|---|
| Body pH | 7.35–7.45 | Lungs (fast) + Kidneys (slow) |
| Blood glucose | 70–99 mg/dL fasting | Insulin (↓glucose) + Glucagon (↑glucose) |
| Core temperature | 36.1–37.2°C | Hypothalamus + skin (sweating/shivering) |
| Blood pressure | 120/80 mmHg | Heart rate + vasoconstriction + fluid volume |
| Serum sodium | 135–145 mEq/L | ADH + aldosterone + thirst mechanism |
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Why this matters for nursing: When you see abnormal labs, ask "What compensatory mechanism has the body activated?" This reveals the severity and trajectory of illness.
Disease Processes
Understanding Disease Processes
| Concept | Definition | Example |
|---|---|---|
| Inflammation | Body's response to injury/infection — redness, warmth, swelling, pain | Cellulitis, appendicitis |
| Ischemia | Insufficient blood flow to tissue | Angina, stroke TIA |
| Infarction | Tissue death from sustained ischemia | MI, ischemic stroke |
| Necrosis | Cell death from disease, injury, or infarction | Pressure injuries Stage III–IV |
| Fibrosis | Scar tissue formation replacing functional tissue | Liver cirrhosis, pulmonary fibrosis |
| Hypertrophy | Increase in cell size | Cardiac hypertrophy from chronic HTN |
| Atrophy | Decrease in cell/organ size | Muscle atrophy from disuse or nerve damage |
| Edema | Fluid accumulation in interstitial space | Heart failure, hypoalbuminemia |
A&P Quick Reference
Quick A&P Reference — The Why Behind Nursing Care
| Nursing Action | A&P Reason Why |
|---|---|
| HOB 30° for tube feeding | Gravity reduces aspiration risk — lower esophageal sphincter works better upright |
| Turn patient q2h | Prolonged pressure compresses capillaries → ischemia → pressure injury |
| Deep breathing after surgery | Anesthesia causes surfactant loss → atelectasis → infection. Deep breathing reopens alveoli |
| Elevate edematous extremity | Gravity assists venous and lymphatic return, reducing hydrostatic pressure |
| Check K+ before digoxin | Low K+ competes with digoxin at Na/K pump → toxicity at therapeutic levels |
| Give iron with vitamin C | Vitamin C converts Fe³⁺ (ferric) to Fe²⁺ (ferrous) — the absorbable form |
| Monitor urine output post-op | Kidneys reflect perfusion — oliguria = low cardiac output or hypovolemia |
📖 Study Notes
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Pathophysiology shortcut: For every disease, ask: What body system? What is failing? What compensatory mechanism is activated? What is the downstream effect on other systems?
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NCLEX application: You do not need to memorize every cellular mechanism. You need to know the CLINICAL PRESENTATION and what nursing action addresses it.
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Inflammation signs: Redness (rubor), Warmth (calor), Swelling (tumor), Pain (dolor), Loss of function. These 5 cardinal signs are the Latin-based classics.