Tissues: The living fabric

Ch 4 c Nervous and Muscle Tissues

Nervous Tissue

Nervous Tissue • Consists of branched neurons with long cellular processes and supporting cells • Supporting cells are nonconducting cells that support, insulate, and protect the delicate neurons.

Nervous Tissue • Neurons transmits electrical signals from sensory receptors to effectors • Found in the brain, spinal cord, and peripheral nerves

Nervous Tissue Figure 4.10

Muscle Tissue

Muscle Tissue • Highly cellular • Well-vascularized • 3 types –Skeletal –Cardiac –smooth

Skeletal Muscle • Long, cylindrical cells, also called muscle fibers • Multinucleated with obvious striations (bands) • Initiates and controls voluntary movement • Found in skeletal muscles that attach to bones or skin

Skeletal muscle tissue • Long, cylindrical, multinucleate cells with obvious striations • Initiates and controls voluntary movement • Found in skeletal muscles that attach to bones or skin Figure 4.11a

Cardiac Muscle Tissue • Branching, striated, uninucleate cells interlocking at intercalated discs • Propels blood into the circulation • Found in the walls of the heart

Cardiac muscle • Branching, striated, uninucleate cells interdigitating at intercalated discs • Propels blood into the circulation • Found in the walls of the heart Figure 4.11b

Smooth Muscle Tissue • Sheets of spindle-shaped cells with central nuclei and no striations • Propels substances along internal passageways (by peristalsis) • Found in the walls of hollow organs

Smooth Muscle Tissue Figure 4.11c

Muscle Tissue • Skeletal muscle is voluntary muscle • Cardiac and Smooth muscles are involuntary muscles

Tissues: The living fabric

Ch 4 d Tissue Repair and Developmental Aspects

What happens when there is trauma to tissue?

Tissue Trauma • Causes inflammation, characterized by: –Dilation of blood vessels –Increase in vessel permeability –Redness, heat, swelling, and pain

Tissue Repair • Severed blood vessels bleed • Inflammatory chemicals are released Figure 4.12a

• Local blood vessels dilate and become • This allows and clotting proteins to site Tissue Repair more permeable white blood cells invade injured Figure 4.12a

Tissue Repair • Clotting proteins initiate clotting, surface dries and forms a scab Figure 4.12a

Tissue Repair • Granulation tissue is formed • Capillary buds invade the clot, restoring vascular supply Figure 4.12b

• Fibroblasts secrete collagen, which bridges the gap • Macrophages phagocytize dead and dying cell debris Tissue Repair Figure 4.12b

Tissue Repair • Surface epithelial cell divide and migrate over the granulation tissue Figure 4.12b

• About one week later, the fibrosed area (scar) has contracted and regeneration of the epithelium is in progress Tissue Repair Figure 4.12c

Tissue Repair • Results in a fully regenerated epithelium with underlying scar tissue Figure 4.12c

Regenerative Capacity • Epithelial tissues, bone, areolar connective tissue, dense irregular connective tissue and blood-forming tissue regenerate extremely well

Regenerative Capacity • Smooth muscle and dense regular connective tissue have a moderate capacity for regeneration

Regenerative Capacity • Skeletal muscle and cartilage have a weak regenerative capacity

Regenerative Capacity • Cardiac muscle and nervous tissue in the brain and spinal cord have NO functional regenerative capacity –They are replaced by scar tissue

Regenerative Capacity • Scar tissue is strong, but lacks flexibility and elasticity of most normal tissues, nor can it perform the normal functions of the tissues it replaced

Developmental Aspects

Developmental Aspects • Primary germ layers: ectoderm, mesoderm, and endoderm Figure 4.13

Developmental Aspects These three layers of cells are formed early in embryonic development then specialize to form the four primary tissues Figure 4.13

Developmental Aspects • Nerve tissue arises from ectoderm (blue) Figure 4.13

Developmental Aspects • Muscle and connective tissue arise from mesoderm (red) Figure 4.13

Developmental Aspects • Most mucous membranes arise from endoderm (yellow) Figure 4.13

Developmental Aspects • Epithelial tissues arise from all three germ layers Figure 4.13

Developmental Aspects • By end of second month of development, all primary tissues have appeared • Tissue cells remain mitotic and produce rapid growth until birth, except the division of nerve cells nearly stop during fetal period

Developmental Aspects • After birth, most tissues divide until adult body size is achieved • In adults only epithelia and blood-forming tissues are highly mitotic

Developmental Aspects • With old age, the amount of collagen declines, making tissue repair less efficient • With old age, bone, muscle, and nervous tissues begin to atrophy

Quiz

next time Study guide check 16-21

Membranes

Cutaneous, Mucous, and Serous

Cutaneous, Mucous, and Serous Membranes • Composed of epithelium tissue bound to connective tissue proper. • Considered simple organs

• Skin • Exposed to air, considered a dry membrane Cutaneous Membranes Figure 4.9a

• Consists of a keratinized stratified squamous epithelium (epidermis) firmly attached to a thick layer of dense irregular connective tissue (dermis) Cutaneous Membranes Figure 4.9a

Mucous Membranes • Lines body cavities open to the exterior (digestive, respiratory, and urogenital tracts) Figure 4.9b

• Epithelial tissue upon a layer of loose connective tissue, then sometimes smooth muscle Mucous Membranes Figure 4.9b

• Considered Wet or moist membranes Mucous Membranes Figure 4.9b

Serous membranes • Moist membranes found in closed ventral body cavities • Simple squamous epithelium resting on a thin layer of loose connective areolar tissue

Serous membranes • Serous fluid lubricates the facing surfaces of the parietal (wall) and visceral (organs).

–Remember this is a double membrane with the serous fluid between the layers

Serous membranes • Serous membranes named according to where they are and the organs they are associated with

Serous membranes • Pleura – lining the thoracic wall and covering the lungs • Pericardium – enclosing the heart • Peritoneums – abdominopelvic cavity and visceral organs