Overview
This lecture covers the four primary types of animal tissues—epithelial, connective, muscle, and nervous—detailing their structure, function, and classification.
Primary Animal Tissues
- Animals have four primary tissue types: epithelial, connective, muscle, and nervous.
- Groups of similar cells form tissues, which combine into organs and organ systems.
Epithelial Tissues
- Epithelial tissue covers organs and lines body surfaces and cavities in single (simple) or multiple (stratified) layers.
- Squamous: Flat, irregular cells; simple in lung alveoli/capillaries, stratified in skin, mouth, vagina.
- Cuboidal: Cube-shaped cells; found in glands and renal tubules.
- Columnar: Tall, narrow cells, absorb nutrients in the digestive tract; pseudostratified forms line respiratory tract.
- Transitional: Round cells, appear layered; found in the bladder and ureter; change thickness with bladder fullness.
Connective Tissues
- Connective tissues contain a matrix (living cells + ground substance) and fibers (collagen, elastic, reticular).
- Loose/Areolar: Loosely arranged fibers; anchors epithelia, surrounds blood vessels.
- Dense (Fibrous): Mostly collagen; irregular forms in skin, regular in tendons/ligaments.
- Cartilage: Chondrocytes make matrix; hyaline (ends of bones), elastic (ears), fibrocartilage (intervertebral discs).
- Bone: Matrix of collagen and minerals; osteoblasts build, osteocytes maintain, osteoclasts break down bone.
- Adipose: Comprised of adipocytes; stores fat, insulates, cushions organs.
- Blood: Matrix is plasma; contains erythrocytes (Oâ‚‚ transport), leukocytes (immune), and platelets (clotting).
Muscle Tissues
- Smooth Muscle: Non-striated, single central nucleus, involuntary, found in internal organs.
- Skeletal Muscle: Striated, multiple peripheral nuclei, voluntary, attached to bones.
- Cardiac Muscle: Striated, single central nucleus, involuntary, found in the heart, contains intercalated discs.
Nervous Tissues
- Nervous tissue composed of neurons (send/receive impulses) and glial cells (support, insulate, protect neurons).
- Neurons have cell bodies, dendrites (receive signals), and axons (send signals).
- Glial cells include astrocytes (regulate environment) and oligodendrocytes (insulate axons).
Key Terms & Definitions
- Epithelium — Tissue covering body surfaces and lining cavities.
- Matrix — Nonliving substance in connective tissue, supports cells.
- Fibroblast — Main connective tissue cell, synthesizes fibers.
- Chondrocyte — Cartilage cell.
- Osteoblast/Osteocyte/Osteoclast — Bone-building, maintaining, and breaking cells.
- Erythrocyte — Red blood cell, carries oxygen.
- Leukocyte — White blood cell, immune response.
- Neuron — Nerve cell transmitting signals.
- Glial cell — Supportive cell in nervous tissue.
- Intercalated disc — Specialized cardiac muscle connection for electrical signal transfer.
Action Items / Next Steps
- Review Table 33.2, 33.3, and 33.4 for tissue types and characteristics.
- Complete the interactive review on epithelial tissues at OpenStax.
- Prepare for questions about tissue structure and function.