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The Human Body Plan Skeletal & Muscular Systems
The Body Tissues
I. The Body Tissues: tissues are a group of similar cells: (we’ll talk about a few)
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muscle (msl) tissue are cells that contract.
3 types of msl tissue: skeletal, cardiac (heart), & smooth
Nervous tissue: cells that receive & transmit messages in the form of electrical impulses called neurons; makes up
the brain & spinal cord.
Connective tissue: cells that bind, support, & protect structures; eg: bones, tendons, ligaments, organ wall fibers, blood, &
others.
II. Skeletal System (see h.o. of skeleton)
The Skeleton = endoskeleton, has 2 major divisions:
1. Axial: skull, ribs, & spinal cord
2. Appendicular: the limbs
A. Functions: provides support & form, Surface for msl attachment, Protect vital organs, Store minerals, Red marrow
produces blood cells.
B. Bone Structure:
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the periosteum covers bone, attaches muscles, where vessels enters the bone
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Hard compact bone:on the outside; gives bone strength
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Spongy Bone: outer ends of the bone, porous, gives bone strength
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marrow (bld forming tissue) on the inside: red & yellow marrow
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Haversian canals : channels in the bone that supply blood vessels
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Osteocytes: bone cells arranged around Haversian canals
Injury & repair: fracture: crack or break; if circulation is maintained & periosteum survives healing occurs
C. Bone Development:
Ossification: becoming bone. Bones may be formed from:
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Cartilage: some remains permanent
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Membrane layers: form flat bones
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Sutures: newborn skulls – irregular seams
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Bone elongation: occurs @ the ends of long bones @ end plates composed of cartilage cells
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growth continues until all cartilage in the epiphyseal plate is replaced.
II. Joints: place where 2 bones meet.
A.
Types
synovial Joints: synovial joints are those in which the articulating bones are separated by a fluid containing joint cavity
1. Fixed: no movement; eg: skull
2. Partially Movable (semi movable): limited movement; eg: vertebrae  ribs  sternum
3. Movable Joints
a) Ball & Socket: rotates; eg: hip & shoulder
c) Angular: wrist & ankle
d) Gliding: eg: hand & foot bones, vertebrae
e) Pivot: eg: head  neck; rotation of forearm
g. saddle: a saddle joint allows movement back and forth and up and down, but does not allow for rotation like a ball and
socket joint.
B. Ligaments: connect bone-bone, can stretch. Lined w/cartilage lubricated by secretions. The knee & shoulder have
cushions called bursae (bursitis)
Arthritis: painful, swollen joints.
1. Rheumatoid Arthritis: immune system begins to attack body tissues; joints become inflamed, swollen, stiff, &
deformed.
2. Osteoarthritis: degenerative joint disease; bone rub against bone
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III. The Muscular System
A. 3 Types
1. Skeletal: aka as striated & voluntary msl; has/many nuclei. The body contain about 656 msls.
2. Smooth: no striation: smooth & involuntary. Visceral; in the walls of blood vessels, G-I tract. One nuclei/cell.
3. Cardiac: heart msl; striated BUT involuntary
Muscles are responsible for all movement of the body
B. Muscular Structure
1.Requires constant supply of O2 & nutrients
2.Motor unit: initiates msl contraction. Involves muscle fibers & nerve cells
3.Msl fibers: consists of myofibrils – thread-like thick & thin protein filaments; thin=actin, thick= myosin
Msl Contraction: when a muscle contracts its working; the actin & myosin filament slide pass each other
shortening. Requires ATP. If a msl is NOT working, it’s not contracting, it’s longer.
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C. Characteristics of Muscle: Skeletal and smooth muscle are elongated. Muscle cell = muscle fiber
Contraction of a muscle is due to movement of microfilaments (protein fibers)
All muscles share some terminology
a. Prefixes myo and mys refer to muscle
b. Prefix sarco refers to flesh
D. Shapes of Muscles:
Triangular- shoulder, neck
Spindle- arms, legs
Flat- diaphragm, forehead
Circular- mouth, anus
E. Skeletal Muscle: most are attached by tendons to bones. Cells have more than one nucleus (multinucleated)
Striated- have stripes, banding, Voluntary- subject to conscious control
Tendons are mostly made of collagen fibers
 Found in the limbs
 Produce movement, maintain posture, generate heat, stabilize joints
F. Cellular Structure of Skeletal Muscle: Each cell (fibre) is long and cylindrical. Muscle fibres are multi-nucleated,
typically 50-60mm in diameter, and up to 10cm long. The contractile elements of skeletal muscle cells are
myofibrils.
G. Skeletal muscle – Summary
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Voluntary movement of skeletal parts
Spans joints and attached to skeleton
Multi-nucleated, striated, cylindrical fibres
H. Muscle Control
Type of
muscle
Nervous
control
Type of
control
Example
Skeletal
Skeletal
Controlled by
CNS
Voluntary
Lifting a
glass
Regulated by
ANS
Involuntary
Heart beating
Controlled by
ANS
Involuntary
Peristalsis
Cardiac
Smooth
1. Types of Responses:
2. Twitcha. A single brief contraction
b. Not a normal muscle function
3. Tetanus
a. One contraction immediately followed by another
b. Muscle never completely returns to a relaxed state
c. Effects are compounded
I. Where Does the Energy Come From? Energy is stored in the muscles in the form of ATP. ATP comes from the breakdown
of glucose during Cellular Respiration. This all happens in the Mitochondria of the cell.When a muscle is fatigued (tired) it
is unable to contract because of lack of Oxygen
J. Exercise and Muscles
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Isotonic- muscles shorten and movement occurs ( most normal exercise)
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Isometric- tension in muscles increases, no movement occurs (pushing one hand against the other)
K. Msl & Bone Movement:
1. Tendon: connect msl to bone.
a. Origin: point where msl attaches to a stationary bone. Eg: biceps msl to shoulder
b. Insertion: point where msl attaches to moving bone. Eg. biceps tendon to radius.
L. Muscle Actions:
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Flexors: msls that bend a joint (biceps)
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Extensors: msls that extend a joint (triceps)
Terms:
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Hyperextension: When a joint is extended past the anatomical position the movement is called
hyperextension.
Abduction: move toward the body’s center
Abduction: move away from the body’s center
Circumduction: the circular motion of a limb
Rotation: motion moves a structure in a rotational motion along a longitudinal axis such as turning your
neck to look at either side.
Inversion- turn sole of foot medially
Eversion- turn sole of foot laterally
Pronation- palm facing down
Supination- palm facing up
Opposition- thumb touches tips of fingers on the same hand
M. Msl Fatigue: msl converts glycogen to glucose for ATP prodxn (nrg); msl fatigue is the inability of msls to contract due to
lack of ATP
N. Exercise: strengthens muscles & helps prevent injuries; not just skeletal msl but heart msl, joints, & ligament
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The Skeletal Muscles: There are about 650 muscles in the human body. They enable us to move, maintain posture
and generate heat. In this section we will only study a sample of the major muscles.
Trapezius: Extend Head, Adduct, Elevate or Depress Scapula
Latissimus dorsi: Extend, Adduct & Rotate Arm Medially
Deltoids: Delts. The deltoid covers the shoulder and has the shape of a delta.
Pectoralis major: “pecs”; flexes, adducts & rotates medially
Biceps brachii: “bis, guns” flexor: flexes elbow
Triceps: “tris”; extensor: extends the elbow
Rectus abdominus: “abs, 6 pack” flexes abdomen
External oblique: compresses abdomen
Forearm msls:
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Flexor Capri: flexes wrist
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Extensor Capri: extends wrist
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Flexor digitorum: flexes fingers
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Extensor digitorum: extends fingers
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Pronator: pronates palm
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Supinator: supinates palm
Gluteus maximus: “glutes”
Quadraceps: “quads” great extensor of the knee/foreleg
Vastus lateralis
Vastus intermedius
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L.
M.
Vastus medius
Rectus femoris (tear drop)
Biceps femoris: flexor: extends thigh & flexes lower leg
Gastrocnemius: plantar: flexes foot & lower leg