Lab 4 Notes: Connective, Muscle Tissues & Integument

Connective Tissue

• Most abundant, widespread, and varied tissue type.
• Components:
  • Cells (few): Fibroblasts, etc.
  • Extracellular Matrix (ECM, a lot):
    • Ground Substance: Proteoglycans, Water
    • Fibers: Collagen, Elastic, Reticular
• Vascularity: Generally vascular, except cartilage (avascular) and dense regular CT (low vascularity).

Connective Tissue Proper

• Excludes bone, cartilage, and blood.
• Classes:
  • Loose Connective Tissue
    • Areolar: Gel-like matrix with all 3 fiber types; wraps/cushions organs; contains fibroblasts, macrophages, mast cells, and some white blood cells.
    • Adipose: Similar matrix to areolar but with closely packed adipocytes; insulates, supports, protects, and stores food reserves.
    • Reticular: Loose ground substance with reticular fibers; forms a soft internal skeleton (stroma) in lymph nodes, bone marrow, and spleen; reticular cells on the network.
  • Dense Connective Tissue
    • Dense Regular: Parallel collagen fibers; fibroblasts are major cell type; attaches muscles to bone or other muscles, and bone to bone; found in tendons and ligaments.
    • Dense Irregular: Irregularly arranged collagen fibers; fibroblasts are major cell type; withstands tension in many directions; found in dermis, submucosa, and fibrous organ capsules.

Specialized Connective Tissues

• Blood: Red and white cells in plasma; transports gases, nutrients, and wastes; contained within blood vessels.
• Cartilage:
  • Hyaline Cartilage: Amorphous, firm matrix; chondrocytes in lacunae; supports, cushions, and resists compression; found in embryonic skeleton, ends of long bones, nose, trachea, and larynx.
• Bone (Osseous Tissue): Hard, calcified matrix with collagen fibers; osteocytes in lacunae; supports, protects, and provides levers for muscular action; stores calcium, minerals, and fat; marrow is site of hematopoiesis.
  • Osteon Structure: lamella(e) (circular), lacuna(e) for osteocyte, Haversian Canal (central; contains vein, nerve and artery).

Muscle Tissue

• Transforms chemical energy (ATP) to directed mechanical energy, exerting force.
• Types:
  • Skeletal: Attached to bone or skin; voluntary; long, multinucleate, striated cells (muscle fibers).
  • Cardiac: Heart; involuntary; striated, long, branching uninucleate cells; has intercalated discs for synchronized contraction.
  • Smooth (Visceral): Walls of hollow organs; involuntary; non-striated, spindle-shaped cells.

Integument (Skin)

Epidermis

• Functions: Making new skin cells, giving skin its color, protecting your body
• Layers (superficial to deep): Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale.
• Melanin: Reddish-yellow to brownish-black pigment, produced in melanocytes, protects against UV radiation.
• Carotene: Yellow to orange pigment from food, accumulates in stratum corneum and hypodermis, can be converted to vitamin A.
• Hemoglobin: Pinkish hue of fair skin.

Skin Cancer

• Risk factors: Overexposure to UV radiation, frequent irritation of skin.
• Types:
  • Basal Cell Carcinoma: Least malignant, most common.
  • Squamous Cell Carcinoma: Involves keratinocytes of stratum spinosum; can metastasize.
  • Melanoma: Cancer of melanocytes; most dangerous, highly metastatic.
    • ABCD Rule: Asymmetry, Border irregularity, Color variation, Diameter >6mm, Evolving.

Dermis

• Functions: Making sweat, Helping you feel things, Growing hair, Making oil Bringing blood to your skin
• Layers:
  • Papillary Layer: Areolar connective tissue with collagen and elastic fibers and blood vessels. Has dermal papillae.
  • Reticular Layer: Dense fibrous connective tissue; elastic fibers for stretch-recoil, collagen fibers for strength, cleavage lines.

Hypodermis (Subcutaneous Layer)

• Attaches the dermis to your muscles and bones
• Helping the blood vessels and nerve cells
• Controlling your body temperature
• Storing your fat