La anatomía estudia la estructura del cuerpo humano, mientras que la fisiología estudia su funcionamiento. Ambas disciplinas son inseparables: comprender por qué el corazón late requiere conocer su estructura. En enfermería, esta base es esencial para interpretar los signos clínicos y planificar cuidados seguros.
- Niveles de organización: químico → celular → tisular → órgano → sistema → organismo
- Homeostasis: mantenimiento de un ambiente interno estable mediante mecanismos de retroalimentación negativa
- Términos direccionales: anterior/posterior, medial/lateral, proximal/distal, ipsilateral/contralateral
- Cavidades corporales: torácica (corazón, pulmones), abdominopélvica, craneal, vertebral
- Los 11 sistemas: tegumentario, óseo, muscular, nervioso, endocrino, cardiovascular, linfático, respiratorio, digestivo, urinario, reproductor
Anatomy & Physiology
Master the structure and function of the human body, from cells and tissues to organ systems, building the foundation for clinical nursing practice.
Structural Organization
Levels of Organization
From atoms to the complete organism
The human body is organized in a hierarchy of increasing complexity. Each level of organization builds upon the previous, with emergent properties at each stage that cannot be predicted from the level below alone.
Chemical
Atoms & molecules
Cellular
Basic unit of life
Tissue
Groups of cells
Organ
Multiple tissues
System
Organs working together
Organism
Complete human
Clinical Connection
Disease can originate at any level and cascade upward. A molecular mutation (chemical level) can impair cell function (cellular), damage tissue, compromise an organ, and ultimately affect the whole organism. Understanding this hierarchy helps you trace symptoms back to root causes.
Anatomical Position & Directional Terms
The universal language of anatomy
All anatomical descriptions reference the anatomical position. Using standardized directional terms ensures clear communication among healthcare providers.
Paired Directional Terms
Superior/Inferior (above/below) • Anterior/Posterior (front/back) • Medial/Lateral (toward/away from midline) • Proximal/Distal (closer/farther from trunk) • Superficial/Deep (surface/internal)
Body Planes & Sections
Sagittal (left/right) • Frontal/Coronal (anterior/posterior) • Transverse/Horizontal (superior/inferior). CT scans typically show transverse sections; MRI can show any plane.
Clinical Communication
Precise anatomical language prevents medical errors. 'The wound is on the medial aspect of the right lower leg, 3 cm distal to the knee' is far more useful than 'the wound is on the inside of the leg near the knee.' Always use directional terms in documentation.
Homeostasis & Feedback Mechanisms
How the body maintains internal stability
Homeostasis is the central organizing principle of physiology. Nearly every disease can be understood as a failure of homeostatic mechanisms.
Negative Feedback (Most Common)
Opposes the initial change, returning the variable toward the set point. Examples: thermoregulation, blood glucose regulation, blood pressure control via baroreceptors.
Positive Feedback (Rare)
Amplifies the initial change until a culminating event occurs. Examples: oxytocin during labor (contractions intensify until delivery), blood clotting cascade, fever in some contexts.
Feedback Components
Every feedback loop has three components: (1) Receptor, detects the change (sensor), (2) Control Center, processes information and determines response (often the brain), (3) Effector, carries out the corrective action (muscle, gland). Failure at any component disrupts homeostasis.
Structure-Function Relationships & Organ Systems
How anatomy dictates physiology
The principle of complementarity of structure and function is fundamental, you can predict a structure's function by examining its anatomy, and vice versa.
11 Organ Systems Overview
Cellular Communication Basics
Cells communicate via direct contact (gap junctions), chemical signals (hormones, neurotransmitters, paracrines), and electrical signals (neurons). Autocrine signals act on the same cell; paracrine signals act on nearby cells; endocrine signals travel via blood to distant targets. Understanding communication modes explains how drugs, diseases, and therapies work at the cellular level.
Directional Terms
Match each directional term to its meaning
Terms
Definitions
Structural Organization Check
1/4Which level of structural organization involves groups of cells working together to perform a specific function?
Cell & Tissue Biology
Cell Membrane Structure
The phospholipid bilayer and membrane proteins
The cell membrane (plasma membrane) is the gatekeeper of every cell, controlling substance movement and enabling cellular communication.
Phospholipid Bilayer
Hydrophilic heads face outward (toward water); hydrophobic tails face inward. This arrangement creates a selectively permeable barrier. Small nonpolar molecules (O2, CO2) pass freely; charged ions and large molecules cannot.
Membrane Proteins
Channel proteins (allow specific ions through), carrier proteins (transport molecules via conformational change), receptor proteins (receive chemical signals), and enzymes. These proteins make the membrane functional.
Cholesterol & Glycocalyx
Cholesterol stabilizes membrane fluidity across temperature changes. The glycocalyx (sugar coat) enables cell recognition, immune function, and protection. Blood type antigens are part of the glycocalyx on red blood cells.
Membrane Transport
Passive vs active transport across the cell membrane
Understanding membrane transport is critical for understanding IV fluid therapy, medication absorption, renal function, and electrolyte balance.
Transport Mechanisms
Electrochemical Gradients
The electrochemical gradient combines the concentration gradient (chemical) with the electrical gradient (charge difference across the membrane). The Na+/K+ pump creates both: more Na+ outside (chemical) and net negative charge inside (electrical). This stored energy drives nerve impulses, muscle contraction, and secondary active transport (e.g., glucose co-transport in the intestine).
Receptors & Cell Signaling
How cells receive and respond to chemical messages
Cell signaling underlies pharmacology, drugs work by mimicking or blocking natural signaling molecules.
Receptor Types
Membrane receptors: G-protein coupled, ion channels, enzyme-linked. Intracellular receptors: for lipid-soluble hormones (steroids, thyroid hormone) that cross the membrane and bind DNA directly.
Signal Transduction
Ligand binds receptor → intracellular cascade → cellular response. Second messengers (cAMP, Ca2+) amplify the signal. One hormone molecule can trigger thousands of cellular reactions through signal amplification.
Drug-Receptor Interactions
Agonists mimic the natural ligand and activate the receptor (e.g., albuterol mimics epinephrine at beta-2 receptors → bronchodilation). Antagonists block the receptor without activating it (e.g., propranolol blocks beta receptors → decreased heart rate). Understanding receptor pharmacology is the foundation of safe medication administration.
Tissue Types
Epithelial, connective, muscle, and nervous tissue
The Four Primary Tissue Types
Cellular Injury & Adaptation
Cells respond to stress through adaptive changes: Atrophy (decreased size, muscle wasting from disuse), Hypertrophy (increased size, cardiac enlargement from hypertension), Hyperplasia (increased number, endometrial thickening), Metaplasia (change in type, smoker's bronchial cells). If stress exceeds adaptive capacity, irreversible injury leads to necrosis (pathological death) or apoptosis (programmed death).
Transport Mechanisms
Match each transport type to its key characteristic
Terms
Definitions
Cell & Tissue Biology Check
1/5A nurse hangs a 0.45% NaCl (hypotonic) IV solution. What will happen to the patient's red blood cells?
Integumentary System
Skin Structure & Protective Functions
The body
The skin is the body's largest organ, comprising about 16% of body weight. It has three primary layers: epidermis, dermis, and the hypodermis.
Protection
Physical barrier against pathogens, chemicals, UV radiation. Acid mantle (pH 4-6) inhibits bacterial growth.
Thermoregulation
Dermal blood vessel dilation/constriction and sweat gland activation regulate body temperature under hypothalamic control.
Sensation & Synthesis
Rich nerve endings detect touch, pressure, temperature, pain. Vitamin D synthesis occurs when UV light hits the epidermis.
Skin Integrity, Wound Healing & Fluid Loss
Maintaining the body
Skin integrity is a critical nursing assessment. Factors that compromise the skin barrier include age (thinner epidermis, less collagen), nutrition (protein/vitamin C deficiency impairs healing), moisture (incontinence-associated dermatitis), pressure (decubitus ulcers), and disease (diabetes impairs microcirculation).
Wound Healing Phases
Skin Turgor & Fluid Assessment
Skin turgor assesses hydration status. When skin is gently pinched and released, well-hydrated tissue returns immediately to its normal position. Tenting (skin remains raised) indicates dehydration, decreased interstitial fluid reduces skin elasticity. Assess on the sternum or inner forearm; elderly patients' decreased collagen makes extremity turgor unreliable. Insensible water loss through the skin is approximately 300-400 mL/day and increases dramatically with burns, fever, and low humidity.
Integumentary System Check
1/3A nurse assesses a patient and finds decreased skin turgor. This finding most likely indicates:
Skeletal System
Bone Structure & Function
Living tissue that supports, protects, and stores minerals
Bones are dynamic living tissue, not static structures. They are continuously remodeled throughout life, responding to mechanical stress, hormonal signals, and nutritional status.
Bone Cells
Osteoblasts BUILD bone (think 'B' for build). Osteoclasts BREAK DOWN bone (think 'C' for consume). Osteocytes are mature bone cells embedded in the matrix that sense mechanical stress and regulate remodeling.
Compact vs Spongy Bone
Compact (cortical) bone: dense outer layer, organized in osteons (Haversian systems). Spongy (cancellous) bone: inner lattice structure (trabeculae), lighter, contains red bone marrow for hematopoiesis in flat bones and epiphyses.
Bone Functions
Support and shape • Protection (skull protects brain, ribs protect heart/lungs) • Movement (muscle attachment) • Mineral storage (calcium, phosphorus) • Blood cell production (hematopoiesis) • Energy storage (yellow marrow = fat).
Calcium Homeostasis & Bone Types
Hormonal regulation and skeletal classification
Calcium homeostasis involves a delicate balance between PTH and calcitonin, with bones serving as the body's calcium reservoir.
PTH (Raises Calcium)
Low Ca2+ → parathyroid glands release PTH → stimulates osteoclasts (bone resorption), increases renal Ca2+ reabsorption, activates vitamin D → calcium rises. Remember: PTH = 'Pulls calcium To High.'
Calcitonin (Lowers Calcium)
High Ca2+ → thyroid C-cells release calcitonin → inhibits osteoclasts, promotes calcium deposition in bone → calcium drops. Calcitonin 'tones down' calcium. Less clinically significant than PTH.
Types of Bones
Long bones (femur, humerus), levers for movement. Short bones (carpals, tarsals), gliding movements. Flat bones (skull, sternum, pelvis), protection and hematopoiesis. Irregular bones (vertebrae, facial bones), complex shapes for specific functions. Sesamoid bones (patella), develop within tendons to reduce friction.
Joints & the Skeleton
Where bones meet and how the skeleton is organized
Joint Classification
Fibrous joints (synarthroses): immovable (skull sutures). Cartilaginous joints (amphiarthroses): slightly movable (intervertebral discs, pubic symphysis). Synovial joints (diarthroses): freely movable (knee, shoulder, hip), most clinically significant.
Synovial Joint Features
Joint cavity with synovial fluid (lubrication, nutrition). Articular cartilage (smooth, shock-absorbing). Joint capsule with ligaments (stability). Menisci and bursae provide additional support. Movements: flexion, extension, abduction, adduction, rotation, circumduction.
Axial vs Appendicular Skeleton
The axial skeleton (80 bones) forms the central axis: skull (22), hyoid (1), vertebral column (26), thoracic cage (25). It protects the brain, spinal cord, and thoracic organs. The appendicular skeleton (126 bones) includes the pectoral girdle, upper limbs, pelvic girdle, and lower limbs, designed for movement and manipulation. Total: 206 bones in the adult skeleton.
Bone & Joint Concepts
Match each term to its description
Terms
Definitions
Skeletal System Check
1/4Which cells are responsible for bone resorption (breaking down bone)?
Muscular System
Muscle Tissue Characteristics
Three types of muscle and their unique properties
All muscle tissue shares four key properties: excitability, contractility, extensibility, and elasticity. However, the three muscle types differ significantly in structure, control, and location.
Skeletal Muscle
Voluntary, striated, multinucleated. Attached to bones via tendons. Under conscious (somatic nervous system) control. Fast contraction but fatigues. Makes up ~40% of body weight.
Cardiac Muscle
Involuntary, striated, branched. Found ONLY in the heart. Intercalated discs allow synchronized contraction. Autorhythmic, generates its own electrical impulses. Highly resistant to fatigue.
Smooth Muscle
Involuntary, non-striated, spindle-shaped. Found in walls of hollow organs (blood vessels, GI tract, bladder, airways). Slow, sustained contractions. Controlled by ANS, hormones, and local factors.
Sliding Filament Theory & Neuromuscular Junction
How muscles contract at the molecular level
Muscle contraction follows the sliding filament theory, which begins with a signal at the neuromuscular junction.
Neuromuscular Junction (NMJ)
Motor neuron releases ACh → ACh binds nicotinic receptors on muscle fiber → depolarization → action potential propagates along sarcolemma and into T-tubules → Ca2+ released from sarcoplasmic reticulum → contraction begins.
Contraction Cycle
Ca2+ binds troponin → tropomyosin shifts → actin binding sites exposed → myosin cross-bridge forms → power stroke (pulls actin) → ATP binds myosin (detachment) → cycle repeats. Ca2+ removal → relaxation.
Types of Contractions & Muscle Fatigue
Isotonic contractions: muscle length changes (concentric = shortening, eccentric = lengthening under tension). Isometric contractions: muscle generates force without length change (holding a heavy object). Muscle fatigue occurs from ATP depletion, lactic acid accumulation, electrolyte imbalances (K+, Ca2+, Na+), and CNS fatigue. Creatine phosphate provides immediate ATP for the first 10-15 seconds of intense activity, then aerobic and anaerobic pathways take over.
Muscular System Check
1/3The sliding filament theory describes muscle contraction as:
Nervous System
Neuron Structure & Electrical Signaling
How nerve cells generate and transmit impulses
Neurons are the functional units of the nervous system, specialized for rapid electrochemical communication.
Neuron Anatomy
Cell body (soma): contains nucleus and organelles. Dendrites: receive incoming signals (input). Axon: conducts action potentials away from soma (output). Myelin sheath: insulating lipid layer that speeds conduction (saltatory conduction between nodes of Ranvier).
Resting Membrane Potential (-70mV)
At rest, the neuron interior is negative relative to outside. Maintained by: Na+/K+ pump (3 Na+ out, 2 K+ in), K+ leak channels (K+ diffuses out), and large intracellular anions. This 'charged' state is the potential energy for signaling.
Action Potential & Synaptic Transmission
The nerve impulse from generation to communication
Action Potential Steps
Synaptic Transmission
When an action potential reaches the axon terminal: (1) voltage-gated Ca2+ channels open, (2) Ca2+ influx triggers vesicle fusion with the membrane, (3) neurotransmitters are released into the synaptic cleft (exocytosis), (4) neurotransmitters bind postsynaptic receptors, (5) excitatory or inhibitory response generated. The signal is terminated by reuptake, enzymatic breakdown, or diffusion. Most psychiatric and neurological drugs target these synaptic mechanisms.
CNS, PNS & the Autonomic Nervous System
Structural and functional divisions of the nervous system
CNS (Brain & Spinal Cord)
Integration and command center. Protected by meninges, CSF, and bone. Processes sensory input, initiates motor output, and manages higher functions (thought, memory, emotion). Damage is often permanent due to limited regeneration.
PNS (Nerves & Ganglia)
Communication lines between CNS and body. Sensory (afferent) division: carries signals TO the CNS. Motor (efferent) division: carries signals FROM the CNS. Includes somatic (voluntary) and autonomic (involuntary) subdivisions.
Sympathetic NS ('Fight or Flight')
Thoracolumbar origin. Releases norepinephrine. Effects: ↑HR, ↑BP, bronchodilation, pupil dilation, ↑blood glucose, blood shunted to muscles, ↓GI motility. Prepares body for emergency action.
Parasympathetic NS ('Rest & Digest')
Craniosacral origin. Releases acetylcholine. Effects: ↓HR, ↓BP, bronchoconstriction, pupil constriction, ↑GI motility/secretion, promotes digestion. Dominates during rest and recovery.
Key Neurotransmitters
Acetylcholine (ACh): muscle contraction, parasympathetic effects, memory. Norepinephrine: sympathetic 'fight or flight,' alertness. Dopamine: reward, movement (Parkinson's = dopamine deficiency). Serotonin: mood, sleep, appetite (many antidepressants target serotonin). GABA: main inhibitory NT (benzodiazepines enhance GABA). Glutamate: main excitatory NT. Endorphins: natural pain relief. Understanding these helps you predict drug effects and side effects.
Nervous System Concepts
Match each concept to its description
Terms
Definitions
Nervous System Check
1/4During an action potential, the rapid depolarization phase is caused by:
Endocrine System
Hormone Signaling & Negative Feedback
Chemical messengers and how the body regulates them
The endocrine system uses hormones for slower but longer-lasting communication compared to the nervous system.
Water-Soluble Hormones
Peptides and proteins (insulin, ADH, oxytocin). Cannot cross cell membranes. Bind surface receptors → second messenger cascade (cAMP). Fast onset, short duration. Cannot be taken orally (digested).
Lipid-Soluble Hormones
Steroids (cortisol, estrogen, testosterone) and thyroid hormones. Cross membranes freely. Bind intracellular/nuclear receptors → alter gene expression. Slow onset, long duration. Many can be taken orally.
Negative Feedback Controls Most Hormones
Rising hormone levels inhibit further release. Example: Thyroid axis, Hypothalamus releases TRH → Anterior pituitary releases TSH → Thyroid releases T3/T4 → Rising T3/T4 levels inhibit TRH and TSH release (negative feedback). In hypothyroidism, low T3/T4 means TSH is HIGH (no feedback inhibition). In hyperthyroidism, high T3/T4 means TSH is LOW (strong feedback inhibition). This logic applies to most endocrine axes.
The Pituitary Gland
The master gland controlling other endocrine organs
The pituitary gland is controlled by the hypothalamus and regulates thyroid, adrenals, gonads, growth, and more.
Anterior Pituitary Hormones
GH (growth), TSH (thyroid), ACTH (adrenals/cortisol), FSH & LH (gonads), Prolactin (milk production). Mnemonic: FLAT PiG, FSH, LH, ACTH, TSH, Prolactin, GH.
Posterior Pituitary Hormones
ADH (antidiuretic hormone): promotes water reabsorption in kidneys, low ADH → diabetes insipidus (dilute urine). Oxytocin: stimulates uterine contractions and milk let-down. Both made in hypothalamus, stored in posterior pituitary.
Insulin, Glucose Regulation & Stress Hormones
Critical metabolic and stress response pathways
Insulin & Glucagon
Insulin (beta cells): released when glucose HIGH → moves glucose INTO cells, lowers blood sugar. Glucagon (alpha cells): released when glucose LOW → stimulates glycogenolysis and gluconeogenesis, raises blood sugar. They work as antagonistic partners to maintain glucose 70-100 mg/dL.
Stress Response Hormones
Acute stress: Adrenal medulla releases epinephrine/norepinephrine (catecholamines) → rapid fight-or-flight response. Chronic stress: HPA axis activates → hypothalamus (CRH) → anterior pituitary (ACTH) → adrenal cortex (cortisol) → elevated glucose, suppressed immunity, protein breakdown.
Clinical Implications of Cortisol
Chronic cortisol elevation (Cushing syndrome): hyperglycemia, immunosuppression, muscle wasting, central obesity, moon face, thin skin, osteoporosis, poor wound healing. Cortisol deficiency (Addison disease): hypoglycemia, hypotension, hyperkalemia, hyponatremia, hyperpigmentation, fatigue. Exogenous corticosteroids (prednisone) mimic cortisol, never stop abruptly (adrenal suppression → adrenal crisis).
Endocrine Concepts
Match each hormone to its primary action
Terms
Definitions
Endocrine System Check
1/4The primary mechanism for controlling most hormone levels in the body is:
Cardiovascular System
Heart Anatomy & Blood Flow Pathway
Four chambers, four valves, two circuits
The heart is a muscular pump approximately the size of a fist, located in the mediastinum of the thoracic cavity. It has four chambers that work in coordinated pairs to maintain two distinct circulatory loops.
Right Side (Pulmonary Circuit)
Right atrium receives deoxygenated blood from the body via the superior and inferior venae cavae. Blood flows through the tricuspid valve into the right ventricle, then is pumped through the pulmonary semilunar valve into the pulmonary trunk and arteries to the lungs for gas exchange.
Left Side (Systemic Circuit)
The left atrium receives oxygenated blood from the lungs via four pulmonary veins. Blood flows through the bicuspid (mitral) valve into the left ventricle, the most muscular chamber, then is ejected through the aortic semilunar valve into the aorta to supply the entire body.
Blood Flow Sequence
Key Anatomical Facts
The left ventricle wall is approximately 3x thicker than the right because it must generate enough pressure to pump blood through the entire systemic circuit. The coronary arteries (right and left) branch from the base of the aorta and supply the myocardium itself with oxygenated blood. The septum separates left and right sides, preventing mixing of oxygenated and deoxygenated blood.
Cardiac Cycle & Blood Vessel Types
Systole, diastole, and the vascular tree
The cardiac cycle includes all events from one heartbeat to the next. The heart's intrinsic conduction system coordinates the rhythmic contractions without requiring external neural input.
Systole (Contraction)
Atrial systole: atria contract, pushing remaining blood into ventricles. Ventricular systole: ventricles contract, AV valves close (S1 “lub”), semilunar valves open, blood ejected into pulmonary trunk and aorta.
Diastole (Relaxation)
Ventricles relax, semilunar valves close (S2 “dub”), AV valves open. Passive ventricular filling occurs (~70% of filling). The heart spends more time in diastole than systole. Coronary perfusion occurs primarily during diastole.
Conduction System
SA node (pacemaker, 60-100 bpm) → AV node (delay) → Bundle of His → right and left bundle branches → Purkinje fibers → ventricular contraction. This intrinsic system allows the heart to beat independently.
Arteries
Carry blood AWAY from the heart. Thick, muscular, elastic walls withstand high pressure. Arteries branch into smaller arterioles, which regulate blood flow to capillary beds via vasoconstriction/vasodilation.
Capillaries
Microscopic vessels with walls only one endothelial cell thick. This is where exchange occurs: O₂ and nutrients diffuse to tissues; CO₂ and wastes diffuse into blood. Connect arterioles to venules.
Veins
Carry blood TOWARD the heart. Thinner walls, lower pressure, larger lumens than arteries. Many contain one-way valves to prevent backflow. Venous return aided by skeletal muscle pump and respiratory pump.
Cardiac Output
Cardiac output (CO) = Heart Rate (HR) × Stroke Volume (SV). Normal resting CO is approximately 5 L/min. Stroke volume is the amount of blood ejected per beat (~70 mL). CO can increase 4-5x during vigorous exercise through increased HR and SV. Blood pressure = CO × peripheral resistance.
Respiratory System
Airways Anatomy & Gas Exchange
From nasal cavity to alveolar diffusion
The respiratory system is divided into the upper respiratory tract and the lower respiratory tract.
Airway Branching (Conducting Zone → Respiratory Zone)
Alveolar Structure
Type I pneumocytes: thin squamous cells forming the gas exchange surface. Type II pneumocytes: secrete pulmonary surfactant, which reduces surface tension and prevents alveolar collapse (atelectasis). Alveolar macrophages: phagocytize inhaled particles and pathogens.
Gas Exchange (External Respiration)
O₂ diffuses from alveoli (high PO₂) into pulmonary capillary blood (low PO₂). CO₂ diffuses from blood (high PCO₂) into alveoli (low PCO₂). Diffusion occurs across the respiratory membrane: alveolar epithelium + shared basement membrane + capillary endothelium (~0.5 μm total thickness).
Ventilation Mechanics
Inspiration is an ACTIVE process: the diaphragm contracts and flattens, external intercostals elevate the ribs, thoracic volume increases, intrapulmonary pressure drops below atmospheric pressure, and air flows IN (Boyle's law). Quiet expiration is PASSIVE: the diaphragm and intercostals relax, elastic recoil of lungs decreases thoracic volume, intrapulmonary pressure rises above atmospheric pressure, and air flows OUT. Forced expiration recruits internal intercostals and abdominal muscles.
Oxygen Transport
~98.5% of O₂ is transported bound to hemoglobin (as oxyhemoglobin, HbO₂) within red blood cells. ~1.5% is dissolved in plasma. Each hemoglobin molecule can carry up to 4 O₂ molecules. CO₂ transport: ~70% as bicarbonate (HCO₃⁻) in plasma, ~23% bound to hemoglobin (carbaminohemoglobin), ~7% dissolved in plasma.
Digestive System
GI Tract Anatomy & Digestion
From mouth to anus — mechanical and chemical breakdown
The gastrointestinal (GI) tract is a continuous muscular tube approximately 9 meters long, extending from the mouth to the anus. The wall of the GI tract has four basic layers: mucosa, submucosa, muscularis externa (smooth muscle for peristalsis), and serosa (outermost protective layer).
GI Tract Organs in Sequence
Liver
Largest internal organ. Produces bile (emulsifies fats for digestion). Metabolizes nutrients absorbed from the GI tract (via hepatic portal vein). Detoxifies substances, synthesizes plasma proteins (albumin, clotting factors), stores glycogen, and produces urea from ammonia.
Pancreas
Dual function organ. Exocrine: secretes pancreatic juice into the duodenum containing digestive enzymes (pancreatic amylase, lipase, trypsinogen, chymotrypsinogen) and bicarbonate (neutralizes gastric acid). Endocrine: islets of Langerhans produce insulin (beta cells) and glucagon (alpha cells).
Gallbladder
Stores and concentrates bile produced by the liver. When fat enters the duodenum, cholecystokinin (CCK) is released, stimulating the gallbladder to contract and release bile through the common bile duct into the duodenum for fat emulsification.
Mechanical vs. Chemical Digestion
Mechanical digestion physically breaks food into smaller pieces without altering chemical composition, includes mastication (chewing), churning in the stomach, and segmentation in the small intestine. Chemical digestion uses enzymes and other chemicals to break covalent bonds in macromolecules: amylase breaks starch into maltose, pepsin/trypsin break proteins into peptides, lipase breaks triglycerides into fatty acids and monoglycerides, and brush border enzymes complete final digestion at the intestinal wall.
Urinary System
Kidney Structure & Urine Formation
Nephron physiology — filtration, reabsorption, secretion
The urinary system consists of two kidneys, two ureters, the urinary bladder, and the urethra. The kidneys are retroperitoneal organs located against the posterior abdominal wall. Each kidney has an outer renal cortex and an inner renal medulla.
Three Processes of Urine Formation
Nephron Components
Glomerulus (capillary tuft enclosed by Bowman's capsule) → Proximal convoluted tubule (PCT) → Descending limb of loop of Henle (permeable to water) → Ascending limb (impermeable to water, actively transports Na+/Cl−) → Distal convoluted tubule (DCT) → Collecting duct → Renal pelvis.
Hormonal Regulation
ADH (from posterior pituitary): increases water reabsorption in collecting ducts, concentrating urine. Aldosterone (from adrenal cortex): increases Na+ reabsorption and K+ secretion in DCT/collecting duct. ANP (from heart atria): promotes Na+ and water excretion, lowering blood volume. Renin-angiotensin-aldosterone system (RAAS): activated by low blood pressure to retain Na+ and water.
Kidney Functions Beyond Urine Formation
The kidneys do far more than produce urine. They regulate blood volume and pressure (RAAS, ADH), maintain electrolyte balance (Na+, K+, Ca²+, phosphate), regulate acid-base balance (H+ secretion, HCO₃⁻ reabsorption), produce erythropoietin (EPO, stimulates red blood cell production), activate vitamin D (calcitriol, for calcium absorption), and perform gluconeogenesis during prolonged fasting.
Body Systems Review
Cardiovascular, Respiratory, Digestive & Urinary Systems Check
1/5Blood returning from the body enters the heart through the:
Organ Systems & Key Functions
Match each organ system to its primary function
Terms
Definitions
Nursing Responsibilities
La enfermera utiliza el vocabulario anatómico para documentar con precisión los síntomas y transmitir información clínica. Identifica los puntos de referencia anatómicos durante la valoración (auscultación, palpación) y orienta su intervención según el sistema afectado. Un conocimiento sólido de la fisiología permite anticipar complicaciones y explicar los cuidados al paciente.
Clinical Pearls
La retroalimentación negativa es el mecanismo homeostático más común: cuando la glucemia aumenta, se secreta insulina para reducirla. En patología, este mecanismo suele estar alterado (p. ej., diabetes). Los términos direccionales evitan ambigüedades en las comunicaciones: decir 'dolor en el cuadrante inferior derecho' es más preciso que 'dolor a la derecha'.
Patient Education
Explicar la estructura y la función de forma sencilla ayuda a los pacientes a entender su enfermedad. Por ejemplo: 'Su corazón es una bomba que envía sangre a todo su cuerpo. Cuando está debilitado, algunos órganos reciben menos oxígeno.' Las explicaciones claras mejoran el cumplimiento terapéutico.
Key Takeaways
- La anatomía (estructura) y la fisiología (función) siempre se estudian juntas en enfermería
- La homeostasis se altera en la mayoría de las enfermedades — identificar qué mecanismo falla orienta los cuidados
- Dominar el vocabulario direccional es indispensable para una documentación y comunicación precisas
- Los 11 sistemas corporales son interdependientes; la afección de uno suele repercutir en los demás