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Overview of Anatomy and Physiology

• Anatomy: Study of the structure of body parts and their relationships to one another.

  • Gross or Macroscopic Anatomy: Study of large, visible structures.

  • Regional Anatomy: Examines all structures in a specific area (e.g., abdomen).

  • Systemic Anatomy: Focuses on a single organ system (e.g., cardiovascular system).

  • Surface Anatomy: Examines internal structures as they relate to the overlying skin.

  • Microscopic Anatomy: Examines structures too small to be seen with the naked eye.

  • Cytology: Microscopic study of cells.

  • Histology: Microscopic study of tissues.

  • Essential Requirements: Requires anatomical terminology, observation, manipulation, palpation, and auscultation.

• Physiology: Study of the function of body parts and how they carry out life-sustaining activities.

  • Subdivisions: Based on organ systems (e.g., renal or cardiovascular physiology); often focuses on cellular and molecular levels.

  • Essential Requirements: Requires understanding of physical principles (electrical currents, pressure, movement) and chemical principles.

• Principle of Complementarity of Structure and Function: Anatomy and physiology are inseparable; function always reflects structure, and what a structure can do depends on its specific form.

Structural Organization of the Human Body

• Six distinct levels of increasing complexity:

  1. Chemical Level: Atoms, molecules, and organelles.

  2. Cellular Level: Single cells.

  3. Tissue Level: Groups of similar cells.

  4. Organ Level: Contains two or more types of tissues.

  5. Organ System Level: Organs that work closely together.

  6. Organismal Level: All organ systems combined to form the whole organism.

Organ Systems of the Human Body

• Integumentary System:

  • Structure: Skin, sweat glands, oil glands, hair, and nails.

  • Function: Forms the external body covering, protects deep tissues from injury, and synthesizes vitamin D.

• Skeletal System:

  • Structure: Bones, cartilage, and ligaments.

  • Function: Protects and supports organs, provides a framework for muscles, serves as the site of blood cell formation (hematopoiesis), and stores minerals.

• Muscular System:

  • Structure: Muscles and tendons.

  • Function: Allows movement and facial expression, maintains posture, and produces heat.

• Nervous System:

  • Structure: Brain, spinal column, and nerves.

  • Function: Acts as a fast-acting control system that activates bodily responses.

• Cardiovascular System:

  • Structure: Heart and blood vessels.

  • Function: Heart pumps blood; blood vessels transport blood throughout the body.

• Endocrine System:

  • Structure: Pineal gland, pituitary gland, thyroid gland, thymus, adrenal gland, pancreas, ovaries, and testes.

  • Function: Glands secrete hormones to regulate growth, reproduction, and metabolism.

• Lymphatic System:

  • Structure: Red bone marrow, thymus, spleen, lymph nodes, and lymphatic vessels.

  • Function: Returns leaked fluid to blood, defends against pathogens, and houses white blood cells involved in immunity.

• Respiratory System:

  • Structure: Nasal cavity, pharynx, trachea, bronchi, and lungs.

  • Function: Keeps blood supplied with oxygen and removes carbon dioxide.

• Digestive System:

  • Structure: Oral cavity, esophagus, stomach, liver, small intestine, large intestine, rectum, and anus.

  • Function: Breaks down food into absorbable nutrients and eliminates indigestible foodstuffs as feces.

• Urinary System:

  • Structure: Kidneys, ureters, urinary bladder, and urethra.

  • Function: Eliminates nitrogenous wastes; regulates water, electrolyte, and pH balance of the blood.

• Male Reproductive System:

  • Structure: Prostate, penis, testes, scrotum, and vas deferens.

  • Function: Production of offspring; testes produce sperm and male sex hormones to deliver sperm to the female reproductive tract.

• Female Reproductive System:

  • Structure: Mammary glands, ovaries, uterine tubes, uterus, and vagina.

  • Function: Production of offspring; ovaries produce eggs and female sex hormones; serves as the site for fertilization and development of the fetus; mammary glands produce milk for newborns.

Requirements and Functions of Human Life

• Functions of Human Life:

  • Organization: Maintaining distinct cellular and systemic structures.

  • Maintaining Boundaries: Plasma membranes separate cells; skin separates the organism from the external environment.

  • Metabolism: All chemical reactions in the body.

  • Catabolism: Breakdown of complex molecules; releases energy ($\text{ATP}$).

  • Anabolism: Synthesis of complex molecules; requires energy ($\text{ATP}$).

  • Responsiveness: Ability to sense and adjust to stimuli (e.g., cold, heat, pain, atmospheric chemicals).

  • Movement: Facilitated by skeletal muscles, joints, and internal smooth/cardiac muscle movements of blood, food, air, and urine.

  • Development: Structural changes occurring throughout life, including differentiation.

  • Growth: Increase in overall body size.

  • Reproduction: Occurs at cellular level via cell division and nuclear division ($\text{mitosis}$) for growth/repair, and at organismal level to produce offspring.

• Requirements for Human Survival:

  • Oxygen: Essential for releasing energy from food; atmospheric air is approximately $20\%$ oxygen.

  • Nutrients: Chemicals required for energy and cell building.

  • Carbohydrates: Major source of energy.

  • Proteins: Required for cell building and cell chemistry.

  • Fats: Long-term energy storage.

  • Minerals and Vitamins: Involved in chemical reactions and structural functions.

  • Water: Most abundant chemical in the body, accounting for approximately $70\%$ of body mass; provides the liquid medium for chemical reactions, secretions, and excretions.

  • Normal Body Temperature: Must stay near $37^\circ\text{C}$ ($98.6^\circ\text{F}$) to maintain proper rates of chemical reactions; extreme deviations cause hyperthermia (fever) or hypothermia.

  • Appropriate Atmospheric Pressure: Column of mercury under standard sea-level atmospheric pressure equals $760\,\text{mm}$; required for adequate breathing and gas exchange in lungs.

Homeostasis and Feedback Mechanisms

• Homeostasis: A dynamic state of equilibrium maintaining relatively stable internal conditions despite external changes, fluctuating around a specific set point.

• Components of Homeostatic Control:

  • Sensor (Receptor): Monitors environment and responds to stimuli.

  • Control Center: Determines set point and receives input from receptor.

  • Effector: Receives signal from control center and executes response to return value to normal range.

• Negative Feedback Loops:

  • Primary mechanism used by the body.

  • Response reduces, resists, or shuts off the original stimulus deviation to return to homeostasis.

  • Examples: Regulation of body temperature, regulation of blood glucose by insulin.

• Positive Feedback Loops:

  • Response intensifies, increases, or exaggerates the change in the original stimulus.

  • Normal only when there is a definite end point, resulting in a change of status rather than immediate return to homeostasis.

  • Examples: Childbirth (labor contractions) and blood clotting.

• Homeostatic Imbalance:

  • Disturbance of homeostasis that increases risk of disease and contributes to changes seen in aging.

  • Overwhelmed negative feedback systems can allow destructive positive feedback mechanisms to take over (e.g., heart failure).

  • PET Scans: Highlight areas of high glucose consumption characteristic of cancerous tissue and metastases.

Anatomical Terminology, Body Planes, and Cavities

• Standard Anatomical Position:

  • Body standing upright, feet slightly apart, palms facing forward with thumbs pointing away from the body.

  • Right and left always refer to the body being viewed, not the observer.

• Directional Terms:

  • Superior / Inferior

  • Anterior (Ventral) / Posterior (Dorsal)

  • Medial / Lateral

  • Proximal / Distal

  • Superficial / Deep

• Regional Terms:

  • Axial Division: Head, neck, and trunk.

  • Appendicular Division: Limbs (arms and legs).

• Body Planes and Sections:

  • Sagittal Plane: Divides body vertically into right and left parts.

  • Midsagittal (Median) Plane: Cut made directly on the midline.

  • Parasagittal Plane: Cut made off-center from the midline.

  • Frontal (Coronal) Plane: Divides body vertically into anterior and posterior parts.

  • Transverse (Horizontal) Plane: Divides body horizontally at a $90^\circ$ angle to vertical into superior and inferior parts (produces cross sections).

  • Oblique Section: Cut made at an angle other than $90^\circ$

• Body Cavities:

  • Dorsal Body Cavity: Protects nervous system.

  • Cranial Cavity: Houses the brain.

  • Vertebral Cavity: Houses the spinal cord.

  • Ventral Body Cavity: Houses internal organs (viscera); split by the diaphragm into:

  • Thoracic Cavity: Divided into two pleural cavities (each enclosing a lung) and the mediastinum (contains pericardial cavity enclosing the heart, plus esophagus and trachea).

  • Abdominopelvic Cavity: Subdivided into Abdominal cavity (stomach, intestines, spleen, liver) and Pelvic cavity (urinary bladder, reproductive organs, rectum). Mapped into $9$ abdominal regions or $4$ abdominal quadrants.

• Serous Membranes (Serosa):

  • Double-layered membranes in ventral cavity separated by serous fluid to reduce friction.

  • Parietal Serosa: Lines internal cavity walls.

  • Visceral Serosa: Covers internal organs.

  • Key Membranes: Pericardium (heart), Pleura (lungs), Peritoneum (abdominopelvic cavity).