Anatomy & Physiology: Cell Structure, Tissues, Integument, and Pathology Study Notes

Resting Membrane Potential

Definition and Key Features

The resting membrane potential is the stable, negatively charged electrical difference across a cell's plasma membrane when the cell is not stimulated.

• Definition: The electrical charge difference across the plasma membrane of a resting (non-stimulated) cell, usually about -70 mV inside compared to outside.

• Ions involved: Sodium (Na+), Potassium (K+), Chloride (Cl-), and negatively charged proteins inside the cell.

• Maintenance: The Na+/K+ pump (actively moves 3 Na+ out, 2 K+ in) and leak channels (especially K+ leakage out of the cell).

Organelles & Functions

Major Cell Organelles

Cells contain specialized structures called organelles that perform essential functions for survival and activity.

• Mitochondria: Powerhouse; produces ATP by cellular respiration.

• Ribosomes: Protein synthesis (free ribosomes → cytoplasmic proteins; bound ribosomes → secreted/membrane proteins).

• Endoplasmic Reticulum (ER):

  • Rough ER: Protein synthesis/modification.

  • Smooth ER: Lipid synthesis, detoxification, calcium storage.

• Golgi apparatus: Modifies, sorts, packages proteins and lipids for transport.

• Lysosomes: Contain digestive enzymes for breakdown of waste.

• Peroxisomes: Detoxify harmful substances, break down fatty acids.

• Cytoskeleton: Shape, movement, intracellular transport (microfilaments, intermediate filaments, microtubules).

• Nucleus: Stores DNA, controls cell activities.

• Nucleolus: Makes ribosomal RNA (rRNA).

• Centrioles: Organize spindle fibers for cell division.

Cell Growth & Reproduction

Mitosis vs Cytokinesis

Cell division is essential for growth, repair, and reproduction. It involves nuclear and cytoplasmic division.

• Mitosis: Division of the nucleus into two identical nuclei (prophase, metaphase, anaphase, telophase).

• Cytokinesis: Division of the cytoplasm to form two daughter cells.

Protein Synthesis

Transcription and Translation

Protein synthesis is the process by which cells build proteins based on genetic instructions.

• Transcription: DNA → mRNA (in nucleus).

  • Product: mRNA.

  • Steps: Initiation (RNA polymerase binds promoter), Elongation (RNA built), Termination (RNA released).

• Translation: mRNA → Protein (at ribosome in cytoplasm).

  • Product: Polypeptide/protein.

  • Steps: Initiation (start codon, ribosome assembles), Elongation (tRNAs bring amino acids), Termination (stop codon, protein released).

• Types of RNA:

  • mRNA: Carries code from DNA.

  • tRNA: Brings amino acids to ribosome.

  • rRNA: Part of ribosome, helps assemble protein.

Histology

Tissue Definition and Epithelium

Histology is the study of tissues, which are groups of cells with a common structure and function.

• Tissue definition: Group of cells with a common structure and function.

• Epithelium General Functions: Protection, absorption, secretion, filtration.

• Classification:

  • Shape: Squamous (flat), Cuboidal (cube), Columnar (tall).

  • Layers: Simple (1 layer), Stratified (multiple).

• Glands:

  • Exocrine: Secrete into ducts (sweat, saliva).

  • Endocrine: Secrete hormones into blood.

Connective Tissue

Connective tissue supports, binds, protects, and stores substances in the body.

• General functions: Support, binding, protection, storage, transport (blood).

• Characteristics: Cells in matrix, varying vascularity.

• Types:

  • Loose CT (areolar, adipose, reticular).

  • Dense CT (dense regular = tendons, dense irregular = dermis, elastic).

  • Cartilage (hyaline, elastic, fibrocartilage).

  • Bone, blood.

Muscle Tissue

Muscle tissue is responsible for movement, posture, and heat production.

• Functions: Movement, posture, heat production.

• Types:

  • Skeletal (striated, voluntary, multinucleate).

  • Cardiac (striated, involuntary, intercalated discs).

  • Smooth (no striations, involuntary, single nucleus).

Nervous Tissue

Nervous tissue enables communication and control throughout the body.

• Functions: Communication, control.

• Cells:

  • Neurons (transmit signals).

  • Neuroglia (support, protect neurons).

Membranes

Types of Body Membranes

Body membranes cover surfaces, line cavities, and protect organs.

• Cutaneous: Skin (dry, outer covering).

• Mucosa: Lines cavities that open to exterior (respiratory, digestive, urinary).

• Serosa: Lines closed body cavities (pleura, pericardium, peritoneum).

Tissue Repair

Repair Processes

Tissue repair involves inflammation, organization, and regeneration or fibrosis.

• Process: Inflammation → organization (granulation tissue forms) → regeneration (epithelial regrowth) or fibrosis (scar tissue).

• Repair depends on tissue:

  • Epithelial, bone, areolar CT regenerate well.

  • Skeletal muscle regenerates poorly.

  • Cardiac and nervous tissue mostly replaced by scar tissue.

Integument (Skin)

Epidermis

The epidermis is the outermost layer of skin, providing protection and sensory functions.

• Cells:

  • Keratinocytes (produce keratin).

  • Melanocytes (produce melanin).

  • Langerhans/dendritic cells (immune).

  • Merkel cells (touch).

• Layers:

  • Stratum basale (mitosis).

  • Stratum spinosum (desmosomes, pre-keratin).

  • Stratum granulosum (keratinization begins).

  • Stratum lucidum (thick skin only).

  • Stratum corneum (dead, keratinized).

Dermis

The dermis is a strong, flexible connective tissue layer beneath the epidermis.

• Characteristics: Strong, flexible CT.

• Layers:

  • Papillary (areolar CT, dermal papillae, capillaries).

  • Reticular (dense irregular CT, glands, hair follicles).

Pigments for Skin Color

• Melanin, Carotene, Hemoglobin.

Hair

• Function: Protection, sensory, temperature regulation.

Nails

• Function: Protect fingertips, aid in grasping.

Glands

• Sebaceous (oil): Lubricate skin/hair.

• Sweat glands:

  • Eccrine (temperature regulation).

  • Apocrine (axillary/genital, odor with bacteria).

• Ceruminous: Earwax.

Skin Cancer

Types and General Terms

Skin cancer is the abnormal growth of skin cells, often due to UV exposure.

• General terms:

  • Benign (non-spreading), Malignant (cancerous, invasive).

  • Metastasis (spread to other tissues).

• Types:

  • Basal cell carcinoma (most common, least malignant).

  • Squamous cell carcinoma (grows rapidly, may metastasize).

  • Melanoma (most dangerous, highly metastatic).

Burns

Degrees of Burns

Burns are classified by depth and severity of tissue damage.

• First degree: Epidermis only, redness, pain.

• Second degree: Epidermis + part of dermis, blisters.

• Third degree: Entire epidermis + dermis destroyed, gray/black, painless (nerve endings destroyed).