Bones, Muscles and Skin

Chapter 32 pages 920 - 945

Axial skeleton – skull, vertebrae and rib cage.Appendicular skeleton – arms, legs, shoulder,

pelvis

Skeletal system functions

• Support and shape

• Protection• Movement• Mineral Storage

(Ca)• Hematopoeisis –

production of blood cells

Bone Structure

• Bones are a network of living cells embedded in a protein mesh that is covered with Calcium phosphate crystals.

Osteoclast – resorbs bone putting Ca+2 in the blood stream

osteoporosis• http://www.youtube.com/watch?v=rH

yeZhcoZcQ

Joints• Places where

bones meet.• Three kinds:• Immovable joints;

skull, teeth, sacroiliac

• Slightly movable joints; vertebrae, lower leg, wrist

• Movable joints; permit movement in more than one direction.

Freely movable joints

• Synovial joints are freely movable.

• Hard, shiny, smooth hyaline cartilage covers the ends of the bone.

• Softer cushioning cartilage is placed between the bones.

• The joint is encased in a sac (bursa) that has a fluid (synovial) circulating within.

• The bones are tied together with tough, collagenous ligaments.

Ligaments

• Ligaments are composed primarily of collagen.

• They connect bones to bones.

• They are connected to bones by fibers that go deep into the bone’s structure.

• When they break they break in the middle

Anterior Cruciate Surgery

• http://www.youtube.com/watch?v=q96M0jRqn7k

Skeletal Muscle Tissue

• Voluntary• Multinucleated, long

(up to 30 cm) fibers.• Striated, can see

definite stripes caused by the overlapping myosin and actin myofibrils.

• Red color comes from myoglobin, a pigment that stores O2.

• Usually attached to bones

Cardiac Muscle Tissue-Found only in the Heart. Striated and branched. Joined

with other muscle cell fibers via intercalated discs. One or two nuclei/cell. Are striated.

Smooth Muscle Tissue.Non-striated. Spindle shaped cells with a single nucleus. Usually

involuntary. Found in the walls of arteries, intestines, the eye, alveoli. Most can function without direct stimulation from the nervous system. Connected to each other by gap junctions

Muscle Fiber Structure.Thick myosin and thin actin myofibrils. Anchored at the Z line in a functional unit called the

Sarcomere.When stimulated, paddles on the myosin attached to sites on the actin and pull causing the whole

sarcomere to shorten.

The Process of Muscle Cell Contraction

• http://www.youtube.com/watch?v=CepeYFvqmk4

The Neuromuscular Junction is bridged by acetylcholine.

Muscles and Movement

• Muscles are attached to bones by tendons.

• Tendon composition is mostly collagen.

• Muscles do their work by contraction.

• Muscles grouped in opposing pairs, what one muscle does the other undoes.

Exercise and Health

• Muscles, the circulatory system, the heart and the lungs respond to regular exercise.

• The system becomes more efficient, with increased size and number of calories.

• This also strengthens bones.

• Astronauts must exercise to maintain their skeletal and muscular systems.

Skin

• Skin is the soft outer covering of vertebrates.

• It is the largest organ of the body with a total area of 20 ft2.

• It is composed of 3 layers, epidermis, dermis and hypodermis.

• The outer layer is composed of dead cells filled with keratin.

• Scanning electron microscope photo of epidermis, 650X

Skin Functions

• Protection: an anatomical barrier from pathogens and chemicals.

• Sensation: various sensory nerves

• Temp. regulation – sweat• Control evaporation• Stores fats and water• Absorbs some O2.• Water resistance. Oily

layer helps us from drying out

Skin Anatomy

• Composed of 3 parts: epidermis, dermis, hypodermis.

• Outer layer is composed of dead, flattened cells filled with keratin.

• Melanocytes, specialized cells in the stratum basale produce melanin which causes the skin to look darker.

EpidermisNote the melanocyte. Stratum basale is the last layer with a blood supply.

Langerhans cells are part of the immune system.

Dermis

• Contains collagen network, blood vessels, nerves and glands.

• Sweat glands help to keep us cool.

• Sebaceous glands secrete oil to keep skin water proof and supple.

• Hair follicles are found here.

• Hair is composed of keratin

Hair follicle

• Hair follicles contain stem cells that help to renew skin and heal wounds.

• Grows fastest in the morning.

• Has an active phase and a resting phase.

• Follicles can be transplanted.

Hair Transplantation

• Can also be used for eyelashes and eyebrows.

• During first 10 days most of transplanted hair falls out.

• Regrowth will occur and by 6 to 9 months the area will be at its best.

Acne

• Trapped bacteria in plugged hair follicles causes acne.

• Most people have at least some acne during adolescence.

• In severe cases antibiotics can be used

Hives

• In an allergic reaction the skin cells produce histamine.

• Histamine is a chemical that causes blood vessels to dialate and tissues to swell.

• This can lead to the bumps associated with hives.

• Poison ivy would be an example

Squiamos – affects the main cells of the epidermis. Can metastatize and affect other organs of the body.

MelanomaMost dangerous type, cancer of the melanocytes. Look for

moles that suddenly change shape and grow and get darker.