Wednesday, December 06, 1995
Chapter 28 selected pages
They must be able to obtain food. Their method is directly dependent on how they can move and what they eat. Methods include sucking stuff through, actively searching, etc. Some SESSILE or immobile must use a method where the food comes to them. They digest food into fat and gylogen for later and current use via specialized structures.
SYMMETRY is the balence within an organism with regard to shape. Mathematically, it is the duplication of one part in another part. ASYMMETRICAL organisms are irregular and are often sessile. RADIAL SYMMETRY is where the organism can be "folded" along many planes which intersect in a common line. The most common symmetry is BILATERAL which has two halves which mirror each other. The terminology in identifying specific areas of these animals are ANTERIOR, front; POSTERIOR, back; DORSAL, top or back side; and VENTRAL, bottom or belly side.
ACOELOMATE organisms have no body cavities. PSEUDOCOELOMIC organisms have a cavity partially lined with mesoderm. A COELOM "is a body cavity complete surrounded by mesoderm."
The body plan is the shape of the organism and is often termed in symmetry defined above with its resective types.
Its functions include protection from the enviroment, especially mechanical; from dehydration; and from infection. It also functions as a sensory and vitamin D production organ. The skin, the largest organ in the body consist of three parts: the epidermis, the dermis, and the subantaneous layer.
The epidermis is the outermost layer where the top dead cells are constantly flaked off and replaced with new ones underneath. A protein, KERATIN, is responsible for waterproofing while MELANIN pigment protects from solar radiation.
The DERMIS is a connective tissue containing cartilege and numerous other stuff. It has sweat glands, HAIR FOLLICLES, sebuleous or oil glands, and nerve cells. It has touch, heat, cold, pain, and depressure nerve cells. It also has tiny muscles at the end of each hair follicle that contracts when it is cold causing goose bumps which stand up the hair which creates dead air space that just happens to be a good insulator.
The subantaneous layer is composed of fat for insulation.
Through bleeding when scraped, the skin heals itself. (See diagrams text 930-931) The burns are catagorized as first degree, damage to the epidermis; second degree, damage to the dermis; and third degree, where the skin is essentially gone. Wrinkles occur as skin loses its elasticity.
It functions as a protective as well as a structural thing. It also aids in movement. They hold the blood cell makers, the red marrow, and they also store minerals such as calcium.
There are two types of skeletons exoskeletons and endoskeletons. Crabs have exoskeletons while humans have endoskeletons
Consisting of the AXIAL SKELETON, the ribs, vertebrae, and cranial units; and the APPENDICULAR SKELETON, the arms and legs with their sockests, the pelvic and shoulder girdles, form the skeleton. Wherever two bones are joined, a JOINT is formed with LIGAMENTS holding them together. With movable joints, there is a BURSA, a sack of cushioning fluid and TENDONS which connect muscles to bones.
Bones are marked with landmarks which are grooves and holes where the blood vessels and nerves come in and by rough spots where the ligaments and tendons attach.
Formation of bones is made by OSTEOBLASTS which exist in embryonic cartilege and form the hard stuff. The bones grow in both lenght and diameter. The outer area is called the COMPACT BONE while the inner more airy stuff is called the SPONGY BONE which is concentrated at the ends. This is not filled with air in major bones but with MARROW. The marrow in the shaft is yellow marrow and hold fat, but at the ends, it is red and produces blood ceslls.
As you age the bone build up with minerals and not enough collagen protein which makes them brittle. This is called osteoporosis.
Injuries to joints can occur by twisting it the wrong way called a sprain and arthritis which inflames the joints by infection, injury, or age.
This is where the bones are connected so you can bend. There are many types of joints. One is the pivot joint at the base of your head which turns on its own axis. Another is the elbow's hinge joint which moves on a plane. The other type of joint is a ball & socket joint which is found on the should and hip.
Around certain joints is a synovial capsule. Contained within it, is ligaments, tendons, nerves and blood vessels. An example of a synovial joint is the knee.
Injury to the joints (knee) can occur: ACL (Anterior Crucited Ligament). The ligament connects the tibia to the femur in the front area. Commonly called a sprain, acute joint damage occurs quickly, is classified in three groups, and is slow to heal. This is because the cells are fed by synovial fluid not blood. Another injury is arthritis.
Proteins contract to make muscles move. They can only contract so are mostly found in antagonist pairs.
SMOOTH MUSCLE, CARDIAC MUSCLE, and SKELETAL MUSCLE are three types of muscles found in humans. The smooth muscle is an INVOLUNTARY MUSCLE that moves slowly. This type of muscle is unstriated and found in organs. Another involuntary muscle is the cardiac muscle which striated and moves quickly. The skeletal muscles are VOLUTARY MUSCLES and are striated and move quickly.
The types of muscles are the Fast Twitch which move quickly and are for sprinting, power, and are anaerobic. The Slow Twitch muscles are endurence muscles and aerobic. The rations between these are genetically determined. A motor unit is a nerve cell and the muscle fibers it ends at. The smaller the unit the more control one has.
The muscles contract by moving smaller MYOFIBRIL fibers. Each of these fibers has proteins of ACTIN and MYOSIN. The myosin is the bigger one that creates crossbridges when calcium trigger to contract. Each group is called a SARCOMERE. The SLIDING FILAMENT theory states that the myosin which is bigger has tiny hires that pull the outer smaller actins inward.
Thicker fibers are stronger when subjected to higher stresses. Muscle cells use anaerobic respiration to supplement aerobic respiration.