Tissues: The living fabric Ch 4 c Nervous and Muscle Tissues

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

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

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

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 Figure 4.12a Severed blood vessels bleed Inflammatory chemicals are released

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

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

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

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

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

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

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

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

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 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

Cutaneous Membranes Figure 4.9a 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)

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

Mucous Membranes 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

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