Tissues

Muscle tissue

• consists of fibrous cells designed for contraction.

• Contraction depends on actin and myosin microfilaments sliding over each other.

• Three types: skeletal, smooth, and cardiac.

Skeletal muscle:

 large cells with many nuclei and mitochondria; collagen fibers connect to tendons; striated and voluntary; impairment causes paresis or paralysis.

Smooth muscle:

small spindle-shaped, nonstriated, involuntary; found in hollow organs, blood vessels, bladder, uterus, intestines, stomach, and exocrine glands; responsible for peristalsis.

Cardiac muscle:

ound only in the heart; branching cells with one nucleus; connected by intercalated disks; has pacemaker cells; striated and involuntary.

Nervous tissue

• Nervous tissue is designed to receive and transmit electrical signals throughout the body.

• Locations: brain, spinal cord, peripheral nerves.

• Two cell types: neurons and neuroglial cells.

Neuroglial cells

• support neurons, do not transmit impulses, isolate conductive membranes, provide framework and nutrients, phagocytize, and are more numerous than neurons.

Neurons

are the longest cells in the body and have three primary parts: perikaryon, dendrites, and axon.

Healing and repair

• Tissue healing and repair includes inflammation, organization, regeneration or fibrosis, and classifications.

• Injury triggers inflammation, then organization, then regeneration or epithelialization and scar tissue.

Inflammation

is a nonspecific response to injury or disease. 

• It involves vasoconstriction followed by vasodilation, edema, clot formation, phagocytosis, and release of histamine and heparin.

Organization

• is the formation of granulation tissue.

• Wound repair begins soon after injury, with phagocytosis and formation of granulation tissue made of collagen fibers and newly branched capillaries.

Regeneration or fibrosis:

•  epithelialization covers granulation tissue, the scab is pushed off, and granulation tissue becomes fibrous scar tissue.

• Adhesions can occur, especially in the abdomen and thoracic cavities.

First-intention healing:

 wound edges are close together, no granulation tissue forms, and there is no scarring.

Second-intention healing:

wound edges are separated and scarring results.