Animal Tissue Types and Components

4.1 Types of Tissues

• Connective tissue binds and supports body parts
• Muscular tissue moves the body and its parts
• Nervous tissue conducts nerve impulses
• Epithelial tissue covers body surfaces and lines body cavities

4.2 Connective Tissue Components

• Connective tissue is made of specialized cells, ground substance, and protein fibers
• Ground substance is noncellular material between cells; its consistency varies from solid (bone) to fluid (blood)
• Three types of protein fibers:
  • Collagen fibers: flexible and strong
  • Reticular fibers: thin, highly branched collagen fibers
  • Elastic fibers: contain elastin, a protein that stretches and recoils

Fibrous Connective Tissue

• Two main forms: loose and dense
• Both contain fibroblasts, separated by matrix (ground substance and fibers)
• Loose fibrous connective tissue includes:
  • Areolar connective tissue
  • Reticular connective tissue
  • Adipose tissue (supports epithelium and many internal organs)
• Dense fibrous connective tissue is found in:
  • Tendons (connect muscles to bones)
  • Ligaments (connect bones to bones)
  • Contains densely packed collagen fibers
• Adipose tissue is loose

Supportive Connective Tissue

• Two major types: cartilage and bone
• Cartilage is more flexible than bone because it lacks mineralization of the matrix
• Cartilage types:
  • Hyaline cartilage: fine collagen fibers (found in the tip of the nose, ends of long bones and the fetal skeleton)
  • Elastic cartilage: lots of elastic fibers (found in the outer ear)
  • Fibrocartilage: strong collagen fibers (found in the disks between vertebrae)
• Bone is the most rigid connective tissue
• Bone matrix is made of collagen and calcium salts, which provide elasticity and strength
• Types of bone tissue: compact and spongy
• Cells called osteoblasts and osteoclasts form the matrix in bone tissue
• Compact bone makes up the shafts of long bones, and consists of cylindrical structural units called osteons

4.3 Muscular Tissue

• Specialized to contract
• Cells are called muscle fibers
• Types: skeletal, smooth, and cardiac

Skeletal Muscle

• Attached to the skeleton by tendons
• Contraction moves the skeleton
• Voluntarily controlled
• Muscle fibers are long; can run the entire length of the muscle, and have multiple nuclei
• Straited, or striped, in appearance

Smooth Muscle

• No striations
• Spindle-shaped cells with one nucleus
• Involuntarily controlled

Cardiac Muscle

• Found only in the walls of the heart
• Striated
• Involuntarily controlled
• Single nucleus
• Cells are connected by intercalated disks

4.4 Nervous Tissue

• Consists of neurons and neuroglia
• Functions in sensory input, integration, and motor output
• Neurons: dendrites, a cell body, and an axon, with dendrites carrying information toward the cell body, the cell body containing the nucleus and organelles, the axon conducting nerve impulses away from the cell body, and some axons being covered in myelin, a fatty substance.
• Nerves are bundles of axons traveling to and from the brain and spinal cord
• Neuroglia: outnumber neurons 9 to 1, supporting and nourishing neurons by taking up more than half the volume of the brain

4.5 Epithelial Tissue

• Made of tightly packed cells
• Lines body cavities, covers body surfaces, and is found in glands
• Anchored by a basement membrane on one side and is free on the other side
• Named for the number of cell layers and the shape of the cells
• Types: simple vs stratified; squamous, columnar, or cuboidal

4.6 Organ Systems, Body Cavities, and Body Membranes

• Organs and cavities are lined with membranes, many of which secrete fluid

• Anatomical terms:

  • Ventral or anterior refers to the front
  • Dorsal or posterior means toward the back
  • Superior means toward the head
  • Inferior means toward the feet

• Organ systems work together to maintain homeostasis

• Body cavities like ventral (thoracic, abdominal, pelvic) are important for organ function

• Membranes (mucous, serous, synovial, meninges) line body cavities and internal spaces of organs

4.7 Integumentary System

• Includes skin and accessory organs (hair, nails, and glands)
• Functions: protects underlying tissue, regulates body temperature, contains sensory receptors.
• Epidermis: stratified squamous epithelium; kerantinocytes, langerhans, melanocytes
• Dermis: thick layer of dense fibrous connective tissue; sensory receptors, glands
• Subcutaneous layer: composed of loose connective tissue and adipose tissue; stores energy, insulates and protects
• Parts of the system: hair, oil glands, sweat glands, nails

4.8 Homeostasis

• Homeostasis is the relatively constant internal environment
• Body systems (nervous, endocrine, etc.) work together to keep conditions like blood glucose, pH, and body temperature within a normal range.
• Mechanisms that maintain homeostasis include negative and positive feedback loops.

Body Systems and Homeostasis

• The nervous system works quickly; The endocrine system works slowly, but its effects have longer duration
• The endocrine system secretes hormones that travel in the blood
• Negative feedback mechanisms are the primary feedback mechanism in the body (output of the system turns down production; temperature regulation is an example)
• Positive feedback mechanisms bring about a change in the same direction as the original stimulus (childbirth is an example)