Chapter 39

SUPPORT SYSTEMS AND

LOCOMOTION

•Animals that lack a hard skeleton may have a

hydrostatic skeleton

•Hydrostatic skeletons act like a garden hose,

stiffening when hydrated and relaxing when

dehydrated

•Hydras, cnidarians and planarians use their

gastrointestinal cavity as a hydrostatic skeleton

HYDROSTATIC SKELETON

•Exo and endoskeletons are made of calcium carbonate

in mollusks and chitin in insects

•Calcium carbonate skeletons grow with the organism

and are largely protective.

•Chitin is jointed and movable, good for movement on

land.

•Vertebrate skeletons are composed of bone tissue and

are highly durable while occupying small amounts of

space

EXO AND ENDOSKELETON

•Humans have close to 350 bones at birth and 206 bones at an adult

•The cartilage built in the mammalian fetus eventually develops into bone.

•The conversion is due to the deposit of calcium salts into the cartilage by osteoblasts.

•Old bone tissue constantly replaces new bone tissue, particularly thanks to large inputs of calcium by the organism

• This is why children require large amounts of milk, but tend to develop lactose intolerance as they grow older

• The bones are done growing; milk is no longer as necessary

HUMAN SKELETAL SYSTEM

•The skull is built to support the brain.

•The major bones of the skull are the cranium,

the nasal bones, maxilla and mandible

•The mandible is the only freely moveable

portion of the skull, allowing for chewing,

formation of air and sound waves, and holds the

teeth

•Cartilage connects the bones in the skull, and

forms the entirety of the outer ear and the

majority of the inner ear.

THE SKULL

•The vertebral column supports the head and trunk and surrounds and protects the spinal cord.

•Vertebrae are separated into three sections making up a single column

• Cervical vertebrate in the neck (7)

• Thoracic vertebrae in the thorax (12)

• Lumbar vertebrae in the small of the back (5)

• 9 vertebrae fuse during development into the sacrum and coccyx, which support the body while sitting.

•Although connected through fibrocartilage, the vertebral discs support the body while allowing for movement and resistance .

VERTEBRAL COLUMN AND RIB

CAGE

•The rib cage emerges from the thoracic

vertebrae and contains the ribs, cartilage and

sternum (breastbone)

•There are twelve pairs of ribs• Seven *true* ribs that attach to the sternum

• Three false ribs attached by cartilage

• Two false *floating* ribs

•The rib cage’s amazing design strongly protects

the heart and lungs while allowing for expansion

of the stomach and lungs

VERTEBRAL COLUMN AND RIB

CAGE

•The pectoral girdle is made up of the clavicle and

scapula

•The scapula is freely moveable, held in place only by

muscles—high range of motion; low stability

•The free range affects the movability of the humerus

bone.

•The humerus is jointly attached to the radius and ulna,

two thin bones that allow the arm to twist.

•The hand contains 27 bones, providing for a huge

variety of motion.

PECTORAL GIRDLE AND ARM

•The pelvic girdle begins with the coxal bones

(hipbones).

•Anchored in the sacrum is the femur bone.

•The femur bone provides strength for the leg.

•It attaches to the tibia and fibula bones at the

patella (kneecap)

•The tibia and fibula attach to the foot bones.

•The foot contains 26 bones, also allowing for the

high range of motion.

PELVIC GIRDLE AND LEG

•Depending on the definition of a muscle there are 650-850

muscles in the human body.

•Bones are only capable of movement because muscles direct

them.

•Muscles follow the rule of antagonistic pairs (or opposite

pairs•Muscles only pull; they cannot push

•Therefore, for every muscle constriction there must be a muscle

relaxation.

•Muscles respond to an impulse from nerves, which trigger the

reaction of sarcomeres.

•Sarcomeres are sections of cells called myosin and actin,

which are responsible for muscle contraction

HUMAN MUSCULAR SYSTEM

•The sarcomere contains a sandwich of proteins that

make up muscle cells (the bread of the sandwich).

•In between the proteins are layers of actin and myosin

filaments.• The myosin are fixed in position within the muscle. They don’t

move

• The two separate sections of actin are moveable.

•During contraction, the muscle “pulls” when actins

reach toward each other, walking along the myosin.

•They are only able to maintain their contraction

momentarily, until the action potential ends, causing

relaxation

HUMAN MUSCULAR SYSTEM

This question is worth an extra 5% on your essay exam

You may check your answers with me ahead of time for a yes or no response as many times as you like.

•When babies are first born, a mother produces “colostrum,” instead of traditional milk. It is also typical in the first week of birth for babies to lose weight. Explain why.

EXTRA CREDIT