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The Skin (Largest organ of the body) is composed of all
four types of body tissues:
EPITHELIUM – lining of organ
CONNECTIVE – made of
collagen and elastin protein fibers
NERVE – transmit impulses
MUSCLE – associated with
hairs
The Skin’s Roles
1. Regulates Body Temperature
A. Blood vessel dilation and constriction
B. Sweat cools the body
2. Protects body from injury and disease
3. Sense Organ
4. Removes waste
products
5. Layer of fat insulates
the body
6. Produces Vitamin D when exposed to sunlight
Structures of the Skin
I. EPIDERMIS
Outer thin layer
A. OUTER LAYER –
Dead cells
B. INNER LAYER –
Living cells
1. MELANOCYTES – Produce melanin (colors and protects skin
by absorbing UV light)
2. KERATINOCYTES – Produce keratin (tough fibrous protein
that waterproofs the skin)
II. DERMIS – inner, thicker layer of skin; contains collagen
fibers, blood vessels, smooth muscle, nerves, sweat glands,
hair follicles, and oil glands
*Sweat Glands Regulate body temperature and excrete wastes
in sweat
*Sebaceous Glands Produce sebum (oily) – Keeps skin flexible
and waterproof
FANCY WORD FOR
FAT!!!!
III. SUBCUTANEOUS LAYER
(hypodermis) –
Below the dermis;
Contains fat which cushions,
insulates, retains heat and stores
energy
HAIR
HAIR FUNCTIONS 1. Protects and provides insulation
2. Prevents particle from entering
the body (in nose and ear)
*Produced from hair follicles in the
dermis
*Hair is dead cells filled with keratin
*Oil glands keep hairs from becoming brittle
OIL
GLAND
HAIR
FOLLICLE
NAILS
Nails form from nail root
Made of keratin
Fingernails
grow 4X as fast
as toenails!
SKIN DISORDERS
CARCINOMAS –
Skin cancers in non-pigmented cells
Usually high cure rate
MALIGNANT MELANOMA –
In pigmented cells
Usually low cure rates
ACNE –Clogged oil duct and infection
PSORIASIS – Inherited; Rapid growth of
Epidermal cells causing scaly white skin
FUNCTIONS OF THE SKELETAL SYSTEM
1. Provides a framework
2. Protects internal organs
3. Efficient movement
4. Produces blood cells
5. Stores minerals
STRUCTURE OF BONE
PERIOSTEUM – Outside
membrane; supplies nutrients
and oxygen to bone
COMPACT BONE Hard layer of bone under the
membrane
SPONGY BONE Less dense bone; adds
strength without mass; under
compact bone at ends of long
bones and in middle of short
flat bones
BONE MARROW
Soft tissue filling center spaces in most large
bones
Two Types:
1. RED MARROW Makes blood cells;
Mainly found in flat bones and ends of long
bones
2. YELLOW MARROW Mainly fat, can make blood cells if needed; in
center of long bones
GREEN BOXES
SHOW MARROW
CAVITY
BONE STRUCTURE
Formation of Bones - Ossification
Bone from cartilage cells which are in protein fibers of tough
collagen and flexible elastin
Immature bones (OSTEOBLASTS)
secrete minerals that replace cartilage in response to force
In compact bone, layers of collagen and calcium salts form around
hollow channels called HAVERSIAN CANALS that contain blood
vessels and nerves
Bone cells are trapped in the rings and are then called
OSTEOCYTES (mature bone cells)
HAVERSIAN
CANAL
OSTEOCYTE
OSTEOCLASTS break down bone so it can be rebuilt by
osteoblasts
Growth Plates
In the ends of long bones
Cartilage grows causing an increase in the
length of the bone
Growth continues until cartilage
is replaced by bone
In adults,
cartilage is still found
in ears, nose, where ribs
attach to sternum
GROWTH PLATES IN THE
HAND AND WRIST
AFFECTS OF AGE ON THE SKELETAL SYSTEM
OSTEOPOROSIS Loss of bone mass;
more common in older
woman
When work of osteoclasts and osteoblasts isn’t balanced,
bones are weakened.
HEALING OF
BROKEN BONES
HUMAN BODY HAS 206 BONES
Two Main Parts 1. AXIAL SKELETON Bones of skull, vertebrae,
ribs and sternum
2. APPENDICULAR
SKELETON Arms, legs, shoulders,
pelvis
JOINTS – Where two bones meet
Can be movable or immovable (fixed)
STRUCTURES OF MOVABLE
JOINTS:
LIGAMENTS (connect bone to bone)
TENDONS (connect muscle to bone)
SYNOVIAL MEMBRANE – produces synovial
fluid to lubricate
BURSA – sac of SYNOVIAL FLUID for shock
absorption and reducing friction
CARTILAGE – end of bones
THREE MAIN TYPES OF JOINTS
1. IMMOVABLE – Little or no
movement – skull
2. SLIGHTLY MOVABLE –
Limited movement- vertebrae
3. FREELY MOVABLE – Allows
Movement in one or more directions:
A. Ball and socket- shoulder
B. Hinge- knee
C. Pivot- neck to head
D. Saddle- thumb
E. Gliding- foot
TYPES OF
MOVEABLE
JOINTS
Pivot - A ring of bone rotating around
another bone. For example, the neck.
Ball-and-Socket - Allows movement in all
directions. For example, the shoulder joint.
Hinge - Allows the joint to bend and
straighten, but does not rotate. For example,
the elbow joint.
Ellipsoid - A less flexible version of the
ball-and-socket joint. For example, the wrist
joint.
Saddle - Fit together to allow all
movements except rotation. For example, the
thumb joint.
Gliding - Two generally flat surfaces
gliding over each other. For example, the
joints between the tarsals of the foot.
COMMON PROBLEMS WITH JOINTS
SPRAINS Injury due to forcible twisting
ARTHRITIS Inflammation of joint
BURSITIS Inflammation of the bursa
RHEUMATOID
ARTHRITIS –
Immune system
attacks joints and
deposits bone in
them
THREE TYPES OF MUSCLE
1. SMOOTH Found in internal organs and blood vessels
Involuntary slow contractions
2. CARDIAC MUSCLE -
Found in heart
Striped (Striated)
Involuntary
interconnected for rhythmic contractions
3. SKELETAL MUSCLE Attached to bones to move them
Voluntary and consciously controlled by the central
nervous system
Striped (Striated)
with dark and light bands
MAKING THE SKELETON MOVE
ORIGIN – End attached to stationary bone
INSERTION – End attached to moving bone which moves toward
the origin
Muscles work in opposing pairs (ANTAGONISTIC)–
FLEXOR – Bends the joint
EXTENSOR – Straightens the
joint
STRUCTURE OF SKELETAL MUSCLES
Skeletal muscle is composed of MUSCLE FIBERS,
Composed of smaller structures
(MYOFIBRILS)
Muscle fiber
Composed of two types of smaller structures (FILAMENTS):
A. Thick Filaments - Protein MYOSIN
B. Thin Filaments - Protein ACTIN
Alternating myosin and actin
give striped appearance of
muscle
SARCOMERE –
Section of myofibril containing actin
and myosin and bound by Z lines
which are discs attached to actin
SLIDING FILAMENT THEORY
Actin filaments slide towards each other during contraction
as myosin heads attach to actin bending inward
MYOSIN
Exercise tones muscle and increases strength by
increasing the size of the fibers
Energy comes from ATP from aerobic cellular respiration
When there isn’t enough oxygen 
Anaerobic respiration 
Lactic acid (causes cramping until more oxygen
is available)
Muscle Injuries
Muscle Sprain – Torn or overly stretched muscle,
ligament or tendon
Muscle Strain – Pulled muscle; overstretching usually
because not warmed up
Tendonitis – Inflammation of tendons