1. Anatomy Unit 5
Skeletal & Muscular
Systems
Quiz #2
Everything You
Need to Know
(1)Bone Injury Basics:
a. Caused by increased weight on the bone.
b. Caused by irregular movement (twisting/rotating/bending).

2. (2)Types of Fractures:
a. Comminuted = Bone fragments into 3 or more pieces.
b. Spiral = Ragged diagonal break.
c. Depressed = Portion of bone pressed inward. Common skull fracture.
d. Transverse = Horizontal clean break.
e. Oblique = Clean diagonal break.
f. Open = Bone breaks through skin.
g. Compression = Bone is crushed into a dust like substance. Common in
those with osteoporosis.
h. Epiphyseal = Break along the epiphyses where cartilage died.
i. Greenstick = Incomplete break of the bone. Common in children.
(3)Bone Repair:
a. The Stages 
i. Hematoma Formation

3. ii. Fibrocartilaginous Callus Formation
iii. Bony Callus Formation
iv. Bone Remodeling
b. Hematoma Formation Details 
i. Blood and tissue pools at site of bone injury.
ii. Bone cells become deprived of nutrition and start dying.
iii. Tissue becomes inflamed.
c. Fibrocartilaginous Callus Formation Details 
i. Capillaries grow into injury site.
ii. Phagocytic cells invade and clean up the tissue/blood debris.
iii. Osteoblasts and Osteocytes rebuild bone.
iv. Collagen fibers reconnect bone pieces.
d. Bony Callus Formation Details 
i. Fibrocartilaginous Callus forms.
ii. Fibro Callus hardens to form a Callus of Spongy Bone.
iii. More collagen and cartilage is secreted to strengthen bone matrix.
e. Bone Remodeling 
i. Excessive bone on the outside removed.
ii. Compact bone laid down to reconstruct bone fully.
(4)Muscle Basics:

4. a. Types = Skeletal, Cardiac, Smooth
b. Cardiac Muscle 
i. Involuntary Movement
ii. Heart contractions
iii. Found in heart
c. Smooth Muscle 
i. Involuntary Movement
ii. Slow movement of digestive, excretory, and respiratory organs
iii. Forces fluids out of body mostly
d. Skeletal Muscle 
i. Mostly Voluntary Movement
ii. On top of bones
iii. Forceful contractions and lifting of body parts
e. Muscle Functions:
i. Body Movement
ii. Maintain Posture
iii. Stabilize Joints
iv. Produce Heat

5. (5)Skeletal Muscle Anatomy:
a. Muscle = Whole Organ
b. Fascicle = Portion of Muscle = Bundle of Muscle Fibers
c. Muscle Fiber = Muscle Cell
d. Myofibril = Organelle inside the Muscle Cell / Fiber
e. Sarcomere = Structure within the Organelle (Myofibril) within the
Muscle Cell (Fiber)
f. Myofilaments = Actin + Myosin = Proteins making up the Sarcomere
g. FOR THE DIAGRAM BELOW YOU SHOULD BE ABLE TO
IDENTIFY ALL THE PARTS:

6. (6)Skeletal Muscle Membranes:
a. Epimysium = The membrane that covers the whole outside of the
muscle organ, holding all of the fascicles together.
b. Perimysium = The membrane that covers a single fascicle, holding all
of the muscle fibers together in a bundle.
c. Endomysium = The membrane wrapped around a single muscle fiber.

7. (7)Muscle Contractions:
a. Also called “The Sliding Filament Theory”.
b. Basic Steps:
i. Message sent from neuron to the muscle.
ii. Neurotransmitter released from neuron.
iii. Neurotransmitter binds to muscle + Depolarization occurs.
iv. Calcium released from the Sarcoplasmic Reticulum + Calcium
binds with Troponin  Actin Exposed
v. Actin + Myosin grab a hold of one another and contract.
c. Detailed Steps:
i. Some voluntary or involuntary response causes a nerve impulse to
be sent down a neuron.
ii. The neurotransmitter, ACH (acetylcholine) is released from the
neuron.
iii. ACH binds with the sarcolemma of the muscle fiber.
iv. The Sodium-Potassium pumps open + Depoarlization occurs down
the sarcolemma of the muscle fiber.
v. Depolarization across the sarcolemma stimulates the sarcoplasmic
reticulum to release calcium ions into the cell.
vi. Calcium binds with troponin.
vii. The structure of troponin-tropomyosin changes.
viii. Actin is exposed.
ix. Myosin releases Phosphate + ADP (forming ATP).
x. Myosin binds to + grabs Actin.
xi. Myosin and Actin slide toward one another = CONTRACTION.
d. Relaxation Steps:
i. ATP binds back with myosin.
ii. Myosin detaches from Actin.
iii. Troponin + Tropomyosin cover up Actin again.
iv. Calcium goes back to the sarcoplasmic reticulum.
v. The muscle fiber’s sarcolemma is repolarized.
e. Why Is It Called The Sliding Filament Theory?
The myofilaments (actin + myosin) slide toward one another.