Study Guide: Cells, Tissues, and the Integumentary System (CH 03-05)

CH 03. Cells: The Living Units

Phases of the Cell Cycle

The cell cycle is a series of events that cells undergo as they grow and divide. It consists of distinct phases, each with specific functions:

• Interphase: The cell grows, replicates its DNA, and prepares for division. Subdivided into G1 (growth), S (DNA synthesis), and G2 (preparation for mitosis).

• Mitosis: The process of nuclear division, followed by cytokinesis (division of cytoplasm).

• Cytokinesis: Physical separation of the cell into two daughter cells.

Phases of Mitosis and Meiosis

Mitosis and meiosis are processes of cell division, but they differ in purpose and outcome:

• Mitosis: Produces two genetically identical daughter cells for growth and repair. Phases: Prophase, Metaphase, Anaphase, Telophase.

• Meiosis: Produces four genetically unique gametes for sexual reproduction. Involves two rounds of division: Meiosis I and II.

• Comparison: Mitosis maintains chromosome number; meiosis halves it.

Cell Growth and Death

• Hyperplasia: Increase in cell number (e.g., tissue growth during development).

• Hypertrophy: Increase in cell size (e.g., muscle enlargement).

• Atrophy: Decrease in cell size or number (e.g., muscle wasting).

Apoptosis vs. Necrosis

• Apoptosis: Programmed cell death, essential for development and tissue homeostasis.

• Necrosis: Uncontrolled cell death due to injury, often causing inflammation.

CH 04. Tissue: The Living Fabric

Epithelial Tissue

Epithelial tissue covers body surfaces and lines cavities, providing protection, absorption, filtration, and secretion.

• Structural characteristics: Closely packed cells, minimal extracellular matrix, avascular, high regenerative capacity.

• Functional characteristics: Forms barriers, controls permeability, produces secretions.

Types of Epithelia

• Simple epithelia: Single layer, specialized for absorption and filtration (e.g., simple squamous in lungs).

• Stratified epithelia: Multiple layers, protection (e.g., stratified squamous in skin).

• Classification: By cell shape (squamous, cuboidal, columnar) and layering.

Glands

• Definition: A gland is a cell or group of cells that produce and secrete substances.

• Exocrine glands: Secrete products into ducts (e.g., sweat glands).

• Endocrine glands: Release hormones directly into the bloodstream (e.g., thyroid gland).

• Multicellular vs. Unicellular: Multicellular glands (e.g., salivary glands) have many cells; unicellular glands (e.g., goblet cells) are single cells.

Classification of Multicellular Exocrine Glands

• Structural: Simple (unbranched ducts) or compound (branched ducts).

• Functional: Merocrine (exocytosis), holocrine (cell rupture), apocrine (partial cell loss).

Connective Tissue

• Common characteristics: Abundant extracellular matrix, varying vascularity, supports and binds other tissues.

• Structural elements: Cells (fibroblasts, chondrocytes, osteocytes), fibers (collagen, elastic, reticular), ground substance.

Types of Connective Tissue

• Loose connective tissue: Areolar, adipose, reticular; supports and cushions organs.

• Dense connective tissue: Dense regular (tendons), dense irregular (dermis), elastic.

• Cartilage: Hyaline, elastic, fibrocartilage; provides support and flexibility.

• Bone: Supports and protects body structures.

• Blood: Transports nutrients and wastes.

CH 05. The Integumentary System

Layers of Skin and Subcutaneous Tissue

• Skin layers: Epidermis (outer), dermis (inner).

• Subcutaneous tissue: Also called hypodermis; consists mainly of adipose tissue, anchors skin to underlying structures.

Epidermis

• Tissue type: Stratified squamous epithelium.

• Major layers: Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (in thick skin), stratum corneum.

• Functions: Protection, water resistance, barrier to pathogens.

Dermis

• Tissue types: Dense irregular connective tissue.

• Major layers: Papillary (loose connective tissue, forms fingerprints), reticular (dense connective tissue, provides strength).

• Functions: Supports epidermis, houses blood vessels, nerves, glands.

Skin Color

• Factors: Melanin (brown pigment), carotene (yellow-orange pigment), hemoglobin (red pigment).

Hair Follicle Structure and Function

• Parts: Root, shaft, bulb, follicle wall.

• Arrector pili muscle: Contracts to raise hair, causing 'goosebumps.'

Hair Regions and Color

• Regions: Medulla (core), cortex (middle), cuticle (outer).

• Hair color: Determined by melanin type and amount.

• Distribution and growth: Varies by age, genetics, hormones.

Nail Structure

• Structure: Nail plate, nail bed, matrix, cuticle.

Sweat and Oil Glands

• Sweat (sudoriferous) glands: Eccrine (all over body, watery sweat), apocrine (armpits, groin, thicker secretion).

• Oil (sebaceous) glands: Secrete sebum, lubricates skin and hair.

• Comparison: Sweat glands regulate temperature; oil glands prevent dryness.

Eccrine vs. Apocrine Glands

• Eccrine: Most numerous, open directly onto skin, important for thermoregulation.

• Apocrine: Located in specific areas, open into hair follicles, activated at puberty.

Functions of Skin

• Protection: Against mechanical, chemical, and microbial damage.

• Regulation: Body temperature via sweat and blood flow.

• Sensation: Contains sensory receptors for touch, pain, temperature.

• Metabolic: Synthesizes vitamin D.

• Excretion: Removes waste products via sweat.