Tissue Types and Functions

Mammals have four basic types of tissue ◦ Epithelial ◦ Connective ◦ Muscle ◦ Nerve Tissue is a collection of cells, organized for a particular function.

Epithelial Tissue Epithelial tissues are packed together in sheets. – Line the body’s surface and openings. Perform many functions – Offers the body a defense Trauma Sun Extreme temperatures Drying Bacterial invasion

Epithelial Tissue Epithelial cells that line the respiratory tract, intestinal tract, urinary and reproductive tracts also provide protection. ◦ Respiratory – cilla Epithelial cells provide secretions ◦ Tears, saliva, mucus, urine, sweat, and milk

Epithelial Tissue Epithealial cells can also absorb materials. ◦ Intestines, lungs, kidneys all absorb materials from the surroinding fluids. Epithelium has no direct blood supply. ◦ Connective tissue provides support, nutrition, and removes waste via the ECF

Epithelial Tissues Epithelial tissues are classified based on their shape. ◦ Simple with one cell layer ◦ Stratified with multiple layers ◦ Transitional with multiple layers There are also descriptive terms for the shape ◦ Squamous (very flat)  Found where there is a need for exchange  Blood vessels  Respiratory system lining

Epithelial Tissues Cuboidal (cube shaped) ◦ Associated with secretion or absorption  Glands and tubules in the kidneys Columnar (more tall than wide) ◦ Associated with secretion or absorption  Glands, stomach and intestines

Integument Skin performs a variety of functions ◦ Keeps damaging agents out of the body ◦ Keeps fluids and nutrients in the body ◦ Specialization of the skin (hair, fur) helps to maintain body temperature. ◦ Detects pain, pressure, and temperature  Sensory organ

Muscle Types Three muscle types -skeletal, smooth, and cardiac Skeletal Muscle -muscle that is attached to the skeletal structure -voluntary control through nerve signals from the nervous system. Smooth Muscle -located in many of the hollow organs of the body, including the GI tract, urinary bladder, blood vessels. -Involuntary muscle

4. Cardiac Muscle -found in the heart -Involuntary muscle 5. Involuntary muscles- function at all times even when the animal is asleep. 6. Voluntary muscles- function when an animal wants to move.

Skeletal Muscle A. Formation -striated voluntary muscle -muscle consists of thousands of muscle fibers (muscle cells) -entire muscle cell is called a myofiber B. Myofiber -myofibers have several nuclei and large mitochondria. -organized in parallel rows -separated by connective tissue that includes blood vessels and nerves.

C. Myofilaments -made up of two proteins, actin and myosin -organized at entire length of muscle cell -contraction happens when the actin and myosin filaments slide along each other -contraction of muscle fibers begin with stimulation from a nerve cell. -Impulses stimulate the release of calcium (stored in endoplasmic reticulum) -Energy is needed for this process -once relaxed, the cell transports calcium back into the ER Muscle

Cardiac Muscle A. Formation -striated, but is involuntary in action. -appearance of cardiac myofilaments is very similar to skeletal muscle B. Function -mechanism is also very similar to the skeletal system, but contain more mitochondria. -muscle contracts on own, but nerve cells help establish rate of contraction. -glucose and oxygen need to be present in order for the heart to beat -Cells are very organized in the action of the heart beating. Electrical signals are sent between cells which allows the heart to function as one unit.

Smooth Muscle A. Formation -lacks striated appearance -still contains actin and myosin filaments, but are not arranged the same as the skeletal muscle. -individual myfibers is a spindle-shaped cell, tapered at each end, with one nucleus. -arranged in sheets around hollow openings like the GI tract. B. Function -contractions may make openings smaller -in blood vessels it is called constriction -in an organ (esophagus) the contraction helps in propelling food toward the stomach. (peristalsis) -automatic nervous system controls the action of smooth muscle.

Porcine Stress Syndrome ◦ Disease in pigs where calcium is not transported back to the ER. Muscles are left stiff. Rigor Mortis ◦ Occurs after death because there is no energy to transport calcium back to the ER. Hypocalcemia (Milk Fever) ◦ Due to a lack of calcium before calving, causes weakness…cow can’t stand. Cured by administration of calcium solution to the bloodstream.