Skeletal
& Muscular System
Body Cavities
p
The body is divided into several cavities
p
It is much easier to study and located organs if
they are divided into different regions of the body
The human body contains:
The ventral
cavity: (ventral means front)
p
Includes the
thoracic cavity, abdominal cavity and the diaphragm
The thoracic
cavity:
p
Includes the
lungs, trachea, esophagus, and heart
Pericardial
cavity: encloses the heart
Abdominal cavity:
p
Includes the
stomach, liver, gall bladder, pancreas, intestines, kidneys, spleen, (and
ovaries and uterus in females)
Body cavities cont.
Dorsal cavity:
(means back)
p
Includes brain and
spinal cord
Cranial cavity:
p
Includes the brain
Spinal cavity:
p
Includes the
spinal cord
The Skeletal System
p
Includes two main
parts
n
Axial skeleton:
skull, vertebral column, sacrum, breastbone, and ribs
n
Appendicular
skeleton: bones of the arms, legs, shoulder, and pelvic bone
Main Functions:
p
Provide support and form
p
Muscle attachment location
p
Protection of delicate organs
p
Storage of minerals
p
Bone marrow produces blood cells
Formation of bone
p
The formation of bone is called ossification
p
There are two ways bones form
Cartilage to bone (babies until 2 months)
Membrane layers to bone (occurs in most flat
bones)
Structure of Bone
p
Periosteum: tough
fibrous material covering the bone that contains blood vessels
p
Compact bone:
located on outer shafts of long bones; extremely hard
p
Haversian canals:
channels formed in long compact bone
p
Osteocytes: bone
cells
p
Bone Marrow:
n
Red: found in
flat bones and some ends of long bones, and vertebrae
p Forms red corpuscles and most white corpuscles
n
Yellow: found in
long bones, mostly fat cells
p Only makes corpuscles in emergency situations
Types of bones
p There are 206 individual bones in the body
n 4 different types:
p Long bones: arms and legs
p Short bones: wrist and ankle bones
p Flat bones: shoulder and cranium
p Irregular bones: vertebrae
§ Sesamoid bones small round nodules that develop a
tendon (example: patella)
Disorder of the Skeletal System
p
Many disorders result from deficiencies in
mineral supply or necessary vitamins or lack of hormones
p
Osteomyelitis general name for a range of
infections of the bone
p
Causes of many infections:
n
Invasion of bacteria (external or internal)
n
Injury to bone due to a hard blow
Joint Disorders
p
Arthritis: disease of the joints
n
Osteoarthritis
p Usually
results from aging (25-50 years old)
p Irritation
of joints caused by wear or abrasion
n
Rheumatoid arthritus
p Severe
from of disease
p 3x
more common in females
p Joints
become swollen and painful due to inflammation of synovial membrane
p Pain
can cause muscle spasms which can cause deformity
p Late
stages cartilage is destroyed and Calcium forms
Injuries of the Skeletal System
p
Dislocation: bone is forced out of its proper
position
p
Sprain: joint is subjected to sudden, unnatural
motion
-tearing of tendons may occur
p
Fractures:
n
Simple: bone breaks but doesnt protrude out of
skin
n
Compound: broken ends of a fractured bone
protrude out of the skin
Examples:
Muscular System
p
Provides movement of the skeleton
p
There are 600 different types of muscle
p
This system makes up half your body weight
Types of Muscles
Skeletal:
attached to bones to move parts of the skeleton
p Voluntary and striated (looks striped under a microscope)
Visceral: found
in the walls of blood vessels, stomach, intestines, and internal organs
p
No striations and
is involuntary
p
Also called smooth
muscle
Cardiac: found in
the heart
p
Striated and
involuntary
The make up of skeletal muscle
p
Muscles are made up of fibers
n
1-80mm in length
n
Each fiber contains myofibrils (which run the
length of the fiber)
n
Myofibrils are bundles of 2 kinds of protein
p Myosin
filaments: thick (10mm)
p Actin
filaments: thin (5mm)
(see the
Inside Story pg. 938)
How muscles are put together
How does the muscle work?
p
When ATP is supplied to a muscle through an
activation of a nerve impulse contraction occurs
p
Nerve contacts to muscles are branched and
stimulate many muscle fibers at once
n
Nerve cells + Muscle cells = MOTOR UNIT
p
When a motor unit is activated is considered
all or none
n
Strength depends on how many motor units are
activated (1 unit will always contract to the same strength every time)
How muscles work (more detail)
Muscle Actions
p
Muscles attach to bone in two places
n
Point of origin: attachment to stationary part
n
Point of insertion: attachment to moveable part
p
Movement of the trunk or limbs are done in pairs
Types of Muscles
Flexors: bend joints (ex. Biceps)
Extensors: straighten joints (ex. Triceps)
Abductors: moves a limb away from body
Adductors: move limb toward body
Types of Contractions
p
Isometric: constant length, no shortening occurs
n
Weight lifter with weight above head
p
Isotonic: constant force, length changes
n
Moving weights
Disorders
p
Seldom involved with infectious disease
p
Usually injured from an external source
n
Over exercise
n
Injury
Types of disorders
p
Pulled tendons
n
Tendon separates
from muscle
p
Contusions
n
Blood vessels
break due to severe blow
n
Discolored,
painful, and swelling
n
Contraction of
muscle is painful
p
Hernia
n
Organ protrudes
through the wall of muscle tissue in which it is housed (usually the abdomen)
p
Muscle
pull/strain
n
Muscle fibers
overstretched or separated