Integumentary System

Layers and Structure of the Skin

The integumentary system consists of the skin and its associated structures. The skin is composed of multiple layers, each with distinct functions and cell types.

• Layers of the Epidermis (Deepest to Superficial):

  • Stratum Basale (germinative): Last mitotic layer, responsible for cell division.

  • Stratum Spinosum

  • Stratum Granulosum

  • Stratum Lucidum: Present only in thick skin (e.g., palms, soles).

  • Stratum Corneum: Most superficial layer.

• Basement Membrane: Separates the epidermis from the dermis.

• Layers of the Skin: Epidermis and dermis.

• Hypodermis: Layer below the skin, not part of the skin; contains adipose tissue.

Cells of the Epidermis:

• Keratinocytes: Most common, produce keratin for protection.

• Melanocytes: Produce melanin pigment, protect against UV radiation.

• Langerhans (dendritic) cells: Immune defense.

• Tactile (Merkel) cells: Sensory reception.

Skin Color and Pigments

• Melanin: Dark pigment, protects from UV light.

• Hemoglobin: Red pigment from blood.

• Carotene: Yellow-orange pigment from diet (e.g., carrots).

Terms for Skin Color:

• Cyanosis: Blue, due to lack of oxygen.

• Pallor: Pale, due to reduced blood supply.

• Erythema: Redness, due to increased blood flow.

• Hematoma: Black-blue, due to broken blood vessels (bruise).

Skin Cancer and Burns

• Basal Cell Carcinoma: Most common skin cancer; arises from basal cells.

• ABCD Rule: Used to assess skin cancer:

  • A: Asymmetry

  • B: Border irregularity

  • C: Color variation

  • D: Diameter (>6mm)

• Types of Burns: First, second, third degree (10, 20, 30 refers to severity).

• Grafts for Third Degree Burns:

  • Autograft: From patient's own body.

  • Allograft: From another person.

  • Xenograft: From another species.

• Main concern for burn patients: Dehydration/fluid loss; treated with IV fluids.

Glands of the Skin

• Sebaceous (oil) glands: Produce sebum.

• Sudoriferous (sweat) glands: Produce sweat for thermoregulation.

Articulation (Joints)

Types and Structure of Joints

Joints, or articulations, are where two bones meet. They are classified by structure and function.

• Structural Types: Fibrous, cartilaginous, synovial, bony.

• Functional Types:

  • Synarthrotic: Immovable (e.g., sutures).

  • Amphiarthrotic: Semi-movable (e.g., pubic symphysis).

  • Diarthrotic: Freely movable (e.g., synovial joints like knees, elbows).

• Parts of a Synovial Joint: Articular cartilage, joint cavity, synovial membrane, ligaments, bursae.

• Ligament: Connects bone to bone.

• Tendon: Connects muscle to bone.

Synovial Movements

• Flexion, extension, supination, pronation, abduction, adduction.

DNA Replication

Mechanism and Enzymes

DNA replication is a semiconservative process, producing two identical DNA molecules from one original molecule.

• Base Pairing Rules: G-C, C-G, T-A, A-T.

• Direction: All strands synthesized 5' to 3'.

• Antiparallel: Each DNA strand runs in opposite directions.

• Enzymes:

  • Helicase: Unwinds DNA.

  • Primase: Synthesizes RNA primer.

  • DNA Polymerase: Adds nucleotides.

  • Ligase: Joins Okazaki fragments.

• Continuous strand: Leading strand synthesized continuously.

• Discontinuous strand: Lagging strand synthesized in fragments (Okazaki fragments).

Example: During replication, the parental DNA strand serves as a template for the new strand, ensuring genetic fidelity.

Skeletal System

Divisions and Bone Structure

The skeletal system is divided into axial and appendicular divisions, each with specific functions and structures.

• Axial Skeleton: Skull, vertebral column, rib cage.

• Appendicular Skeleton: Limbs, girdles.

• Compact Bone: Contains osteons; dense and strong.

• Spongy Bone: Contains trabeculae; lighter and porous.

• Parts of a Long Bone: Diaphysis, epiphysis, metaphysis, medullary cavity, periosteum.

Bone Cells and Ossification

• Osteoblast: Bone-forming cell.

• Osteoclast: Bone-resorbing cell.

• Osteocyte: Mature bone cell.

• Osteoprogenitor: Stem cell for bone.

• Ossification: Formation of bone.

  • Endochondral: From hyaline cartilage (most common).

  • Intramembranous: From membrane (forms spongy bone).

• Bone Shapes: Long (femur), short (carpals), flat (skull), irregular (vertebrae).

• Red Bone Marrow: Myeloid tissue; forms red blood cells.

Bone Disorders and Hormonal Regulation

• Osteoporosis: Decreased bone density.

• Osteopenia: Decreased ossification.

• Osteosarcoma: Bone cancer.

• Osteomyelitis: Bone inflammation.

• Rickets, Paget's disease: Bone disorders.

• Fracture Types: Hairline, avulsion, greenstick.

• Hormones:

  • Calcitonin: Lowers blood calcium by stimulating osteoblasts.

  • Parathyroid hormone (PTH)/Calcitriol: Raises blood calcium by stimulating osteoclasts.

  • Estrogen: Maintains bone density.

  • Human Growth Hormone (HGH): Stimulates bone growth.

• Epiphyseal Plate: Growth plate in children; becomes epiphyseal line in adults.

• Perichondrium: Membrane surrounding cartilage.

Histology (Tissues)

Types and Characteristics of Tissues

A tissue is a group of cells with a common function. The body has four main tissue types.

• Epithelial: Covers surfaces, lines cavities, forms glands.

• Connective: Supports, binds, protects; most common, vascular (except cartilage, ligaments, tendons).

• Muscular: Contracts to produce movement.

• Nervous: Conducts electrical impulses.

Connective Tissue Components: Cells and matrix (ground substance and fibers).

• Matrix: Can be liquid (blood), gel, or hard (bone).

• Fibers: Collagen (main protein), reticular, elastic.

Cell Junctions and Origin

• Desmosome: Zip-like, strong adhesion.

• Gap junction: Communication.

• Tight junction: Prevents leakage.

• Mesenchyme: Embryonic tissue origin of all connective tissues.

Types of Connective Tissue

• Blood: Only fluid connective tissue.

• Adipose: Fat storage.

• Cartilage: Hyaline (nose, ends of long bones), elastic (ear), fibrocartilage (vertebrae, TMJ).

• Dense regular: Ligaments, tendons.

• Dense irregular: Areolar tissue.

Types of Epithelial Tissue

• Simple squamous: One layer, flat cells; diffusion (lungs).

• Stratified squamous: Multiple layers; protection (skin, esophagus).

• Pseudostratified ciliated columnar: Goblet cells produce mucus; found in trachea.

• Cuboidal: Secretion/absorption; kidneys.

Glands and Vascularity

• Endocrine gland: Ductless, produces hormones.

• Exocrine gland: Has ducts, secretes enzymes, oils, sweat, saliva.

• Avascular: No blood supply (epithelial, cartilage, ligaments, tendons).

• Vascular: Has blood supply (most connective tissues).

Special Terms

• Apoptosis: Programmed cell death.

• Goblet cells: Produce mucus, part of columnar cells.

• Cilia: Movement of substances.

Lab Review: Bones and Tissues

Skull and Bone Landmarks

• Foramen magnum: Large hole for brain/spinal cord.

• Sphenoid: Butterfly-shaped bone inside skull.

• Ethmoid: Behind frontal, in front of sphenoid.

• Conchae: Nasal bones.

• Zygomatic process: Cheek bone.

• Mandible: Lower jaw; condyle part of TMJ.

• Occipital: Back of head.

• Styloid/mastoid: Under skull, sides.

• Sutures: Coronal, etc.

• Perpendicular plate: Nasal structure.

• Temporal: Temple region.

• Lacrimal: Inside eye orbit, near nose.

• Hip bone: Ischium, pubis, ilium.

• Scapula: Shoulder blade.

• Glenoid cavity: Articulates with humerus.

• Maxilla: Upper jaw.

• Carpal bones: Wrist bones (trapezium, etc.).

• Clavicle: Collar bone.

• Humerus: Arm bone.

• Radius: Forearm, thumb side.

• Ulna: Forearm, pinky side.

• Femur: Thigh bone.

• Tibia: Large leg bone.

• Fibula: Small leg bone.

Sections or Planes of the Body

• Coronal (frontal): Divides anterior/posterior.

• Transverse (horizontal): Divides superior/inferior.

• Sagittal (vertical): Divides right/left (medial = equal, parasagittal = unequal).

Osmosis and Cell Solutions

• Osmosis: Movement of water from high to low concentration (passive).

• Hypertonic: Water moves out, cell shrinks (2% NaCl).

• Hypotonic: Water moves in, cell swells (distilled water).

• Isotonic: No net movement (.9% NaCl).

Comparison Table: Epithelial vs. Connective Tissue

DNA Replication: Key Steps and Enzymes

Key Terms and Definitions

• Antagonistic: Opposing actions (e.g., calcitonin vs. PTH).

• Apoptosis: Programmed cell death.

• Sebaceous: Oil gland.

• Sudoriferous: Sweat gland.

• Pilus: Hair.

• Vascular: Has blood supply.

• Sinus: Air-filled cavity in bone.

• Foramen: Hole in bone for vessels/nerves.

• Interstitial: Growth within tissue.

• Hairline: Thin bone fracture.

• Osteosarcoma: Bone cancer.

• Endothelium: Epithelial lining of blood vessels.

Formulas and Equations

• Osmosis: Water movement across a semipermeable membrane from high to low concentration.

• DNA Replication Direction:

• Base Pairing:

Reflex Arc

Components of a Reflex Arc

• Receptor (sensory)

• Afferent nerves (sensory, ventral nerve)

• CNS (brain/spinal cord)

• Efferent nerves (motor, cranial/spinal branches)

• Effector (muscle/gland)

Example: Knee-jerk reflex involves all five components.

Synapse

A synapse is the junction where communication occurs between two neurons, typically via neurotransmitter release, but the cells do not physically touch.

Test Format and Study Tips

• Multiple choice, matching, essays, labeling.

• Essays may include feedback loops for calcium regulation and comparison of tissue types.

• Lab tests include labeling bones, tissues, and anatomical planes.

Additional info: For detailed tissue images and bone labeling, refer to textbook pages and lab materials as indicated.