231 Chapter 1 - 3 (2025) (1)

Chapter 3: Cells - The Living Units

Necessary Life Functions

• Maintaining Boundaries

  • Separation between internal and external environments is crucial.

  • Plasma membranes separate individual cells.

  • Skin acts as a barrier separating the organism from the external environment.

• Movement

  • Muscular system facilitates movement:

    • Movement of body parts via skeletal muscles.

    • Movement of substances via cardiac muscle (blood) and smooth muscle (digestion, urination).

    • Contractility refers to movement at the cellular level.

• Responsiveness

  • Ability to sense and respond to stimuli:

    • Example: Withdrawal reflex prevents injury.

    • Control of breathing must adjust in response to different activities.

• Digestion

  • Breakdown of ingested foodstuffs followed by absorption of simple molecules into blood.

Additional Life Functions

• Metabolism

  • Entirety of chemical reactions occurring in body cells.

  • Comprises of:

    • Catabolism: Breakdown of molecules.

    • Anabolism: Synthesis of molecules.

• Excretion

  • Removal of waste products from metabolism and digestion:

    • Urea from protein breakdown.

    • Carbon dioxide from metabolic processes.

    • Feces from unabsorbed food.

• Reproduction

  • Cellular level reproduction involves cell division for growth or repair.

  • Organismal level reproduction is producing offspring.

• Growth

  • Increase in size of a body part or the entire organism.

Levels of Structural Organization

1. Chemical Level

   • Atoms combine to form molecules.

2. Cellular Level

   • Cells consist of molecules.

   • Example: Smooth muscle cell.

3. Tissue Level

   • Tissues are groups of similar cells.

   • Types: Smooth muscle tissue, connective tissue, epithelial tissue.

4. Organ Level

   • Organs are made of different types of tissues.

   • Example: Blood vessels.

5. Organ System Level

   • Organ systems consist of different organs that work together closely.

6. Organismal Level

   • The entire human organism consists of various organ systems, such as the cardiovascular system.

Body Planes and Sections

• Internal Body Structures

  • Observed through sections/cuts along imaginary lines.

  • Sagittal Section: Divides the body into right and left halves.

    • Midsagittal: Equal right and left halves.

  • Frontal Section: Divides the body into anterior and posterior parts (coronal section).

  • Transverse Section: Divides body into superior and inferior parts (cross section).

Body Quadrants

• Upper Right Quadrant (RUQ)

• Upper Left Quadrant (LUQ)

• Lower Right Quadrant (RLQ)

• Lower Left Quadrant (LLQ)

Regional Descriptions

• Umbilical Region

• Epigastric Region: Superior to umbilical

• Hypogastric (Pubic) Region: Inferior to umbilical

• Right and Left Iliac (Inguinal) Regions: Lateral to hypogastric region

• Right and Left Lumbar Regions: Lateral to umbilical region

• Right and Left Hypochondriac Regions: Lateral to epigastric region

Regions and Organs

• Diaphragm - Muscle separating thoracic and abdominal cavities.

• Liver, Stomach, Gallbladder: Organs located in various regions.

• Ascending and Descending Colon of Large Intestine

• Small Intestine

• Urinary Bladder

Clinical Application: NG Tube Placement

• Assessment of placement in pediatric NG feeding.

• Use a 5-10 cc bolus of air to evaluate tube position by listening for a "pop" in the stomach.

• Important anatomical landmarks are used for placement of a stethoscope.

Body Cavities and Their Subdivisions

• Dorsal Body Cavity:

  • Cranial Cavity (contains brain).

  • Vertebral Cavity (contains spinal cord).

• Ventral Body Cavity:

  • Thoracic Cavity (contains heart and lungs).

  • Superior Mediastinum, Pleural Cavity, Pericardial Cavity within Mediastinum.

  • Abdominal Cavity (contains digestive viscera).

  • Pelvic Cavity (contains urinary bladder, reproductive organs, rectum).

Tissue Organization Layers

• Epithelium: Covering and lining tissues.

• Basement Membrane: Structural layer providing support.

• Connective Tissue: Provides packing and support.

• Muscle: Responsible for movement.

Epithelium and Connective Tissue Layers

• Single epithelial layers forming linings in organ structures (e.g., blood vessels, esophagus).

Homeostasis

• Definition: Maintenance of stable internal conditions despite external changes.

• Regulators: Primarily the nervous and endocrine systems.

• Variables: Factors like blood sugar, body temperature, etc.

• Receptor: Monitors environment and responds to changes.

• Control Center: Evaluates input and determines response.

• Effector: Executes response to return variable to homeostatic level.

Homeostatic Control Mechanisms

• Negative Feedback: Shuts off or reduces original stimulus. Works like a thermostat in maintaining balance.

• Positive Feedback: Enhances or amplifies the original stimulus (e.g., blood clotting process).

Body Systems Overview

• Digestive System: Processes nutrients and éliminates waste.

• Respiratory System: Exchanges oxygen and carbon dioxide.

• Cardiovascular System: Distributes nutrients and waste through the blood.

• Urinary System: Eliminates nitrogenous wastes.

• Integumentary System: Protects the body from the external environment.

Water as Solvent and its Importance

• Osmolarity: Amount and concentration of all solutes in a solution.

• Osmosis: Movement of water across semi-permeable membranes.

• Tonicity: Determines whether cells gain or lose water.

  • Isotonic: Equal concentration with the cytoplasm.

  • Hypotonic: Lower solute concentration than the cytoplasm.

  • Hypertonic: Higher solute concentration than the cytoplasm.

Membrane Transport Mechanisms

• Passive Transport: No energy required, movement down concentration gradients.

• Active Transport: Energy required to move substances against their concentration gradients.

• Transport Types: Uniporters, symporters, antiporters.

Cellular Components: Structure and Function

• General Cell Structure: Includes chromatin, nucleus, plasma membrane, organelles (mitochondria, Golgi apparatus).

• Plasma Membrane Functions:

  • Mechanical barrier, selective permeability, maintains electrochemical gradients, communication.

• Membrane Proteins: Facilitate various functions (transport, signaling, attachment, enzymatic activity).

Cytoskeleton Functionality

• Provides structural support and organization to cells.

• Comprises microfilaments (actin), intermediate filaments, and microtubules (tubulin).

Summary of Water Properties

• Thermal Stability: Water's high heat capacity allows it to stabilize internal temperatures efficiently.