Diffusion and Osmosis

Diffusion

Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration. This process is fundamental for the transport of substances within biological systems.

• Occurs in liquids and gases, but not in solids due to fixed molecular positions.

• Permeability: A membrane must be permeable for diffusion to occur; impermeable membranes prevent diffusion.

• Temperature effect: Higher temperatures increase molecular vibration and diffusion rate.

Osmosis

Osmosis is the movement of water molecules across a selectively permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration).

• Essential for maintaining cell volume and fluid balance.

Types of Solutions and Effects on Cells

• Isotonic Solution: Equal solute concentration inside and outside the cell; no net water movement.

• Hypertonic Solution: Higher solute concentration outside the cell; water moves out, causing the cell to shrink (crenation).

• Hypotonic Solution: Lower solute concentration outside the cell; water moves in, causing the cell to swell and possibly burst (lysis).

Example: Red blood cells in different solutions demonstrate these effects: swelling in hypotonic, shrinking in hypertonic, and maintaining shape in isotonic solutions.

Cell Structure and Function

Plasma Membrane

The plasma membrane is a thin, flexible barrier that surrounds the cell, controlling the movement of substances in and out.

• Acts as a boundary between the cell's internal environment and the external world.

Nucleus and Nucleolus

• Nucleus: The control center of the cell, containing genetic material (DNA) and directing cellular activities such as growth and reproduction.

• Nucleolus: Located inside the nucleus, responsible for ribosome production.

Chromosomes

• Structure: DNA tightly packed with histone proteins.

• Function: Carry genes that encode instructions for protein synthesis.

• Human cells: 46 chromosomes (23 pairs).

Cytoplasmic Organelles

• Ribosomes: Sites of protein synthesis, composed of rRNA and proteins.

• Rough Endoplasmic Reticulum (ER): Studded with ribosomes; synthesizes and processes proteins.

• Smooth Endoplasmic Reticulum (SER): Involved in lipid synthesis, detoxification, and storage.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for delivery.

• Mitochondria: Powerhouse of the cell; site of ATP production via cellular respiration.

• Centrioles: Organize microtubules and play a role in cell division.

• Microvilli: Increase surface area for absorption.

Example: The mitochondria convert glucose into ATP, providing energy for cellular processes.

Cell Cycle

Interphase

Interphase is the period of cell growth and DNA replication, preparing the cell for division.

• G1, S, G2 phases: Cell grows, duplicates organelles, and replicates DNA.

• Nuclear envelope is intact, and DNA is in chromatin form.

Mitosis (M Phase)

Mitosis is the process by which a cell divides to produce two genetically identical daughter cells.

• Prophase: Chromatin condenses into visible chromosomes; nuclear envelope breaks down; spindle fibers form.

• Metaphase: Chromosomes align at the cell's equator.

• Anaphase: Sister chromatids separate and move to opposite poles.

• Telophase: Nuclear envelopes reform; chromosomes decondense; cytokinesis divides the cytoplasm.

Example: Skin cells undergo mitosis to replace damaged or dead cells.

Anatomical Terminology

Regional Terms

Regional terms specify distinct areas of the body, aiding in precise anatomical description.

• Cephalic: Head

• Facial: Face

• Thoracic: Chest/ribcage

• Abdominal: Abdomen/torso

• Pelvic: Hips

• Upper limb: Arm regions (e.g., brachial, antecubital, carpal)

• Lower limb: Leg regions (e.g., femoral, crural, tarsal)

Body Positions

• Prone: Lying on the stomach

• Supine: Lying on the back

Directional Terms

• Anterior (ventral): Front of the body

• Posterior (dorsal): Back of the body

• Medial: Toward the midline

• Lateral: Away from the midline

• Superior: Above

• Inferior: Below

• Proximal: Closer to the point of attachment

• Distal: Farther from the point of attachment

• Superficial: Closer to the surface

• Deep: Further from the surface

Body Planes

• Frontal (coronal): Divides body into anterior and posterior

• Transverse (horizontal): Divides body into superior and inferior

• Sagittal: Divides body into left and right

• Mid-sagittal: Divides body into equal left and right halves

• Parasagittal: Divides body into unequal left and right portions

• Oblique: Slanted division

Tissues

Epithelial Tissue

• Function: Lines surfaces and cavities; forms glands.

• Types: Simple (one layer), stratified (multiple layers).

• Shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

Connective Tissue

• Function: Supports, binds, and protects organs.

• Types: Bone (hard, calcified), cartilage (soft, cushioning), blood (cells in plasma), lymph (fluid outside blood vessels).

• Tendons: Connect muscle to bone.

• Ligaments: Connect bone to bone.

Muscle Tissue

• Cardiac: Striated, single nucleus, involuntary, found in heart.

• Skeletal: Striated, multiple nuclei, voluntary, attached to bones.

• Smooth: Non-striated, spindle-shaped, involuntary, found in walls of organs.

Nervous Tissue

• Neurons: Specialized for communication and coordination of body functions.

Integumentary System

Structure

• Cutaneous membrane: Skin

• Accessory structures: Hair, nails, sweat glands, etc.

Layers of the Skin

• Epidermis: Epithelial tissue; layers include (from superficial to deep):

  • Stratum corneum

  • Stratum granulosum

  • Stratum spinosum

  • Stratum basale

  • Stratum lucidum (only in thick skin)

• Dermis: Connective tissue; contains papillary (superficial) and reticular (deep) layers, sensory receptors (Meissner's and Pacinian corpuscles), sebaceous (oil) and sudoriferous (sweat) glands.

• Hypodermis: Deepest layer; connects skin to underlying tissues.

Hair Structure

• Hair follicle: Anchors hair in skin.

• Hair bulb: Base of follicle; site of hair growth.

• Hair papilla: Supplies nutrients to growing hair.

• Arrector pili: Muscle that causes hair to stand up.

Example: The epidermis provides a barrier to pathogens, while sweat glands help regulate body temperature.

Additional info: Some tissues, like cartilage, heal slowly due to lack of blood supply, while bone heals faster because it is vascularized.