Muscular and Skeletal SystemPowerpoint #2
Unit 8 – Chapters 35/36
Working together to create movement
Skeletal System
Structures: Bones CartilageLigaments Tendons
Skeletal SystemFunction:
Supports bodyProtects internal organsAllows for movementStores mineral reservesProvides a site for blood cell formation
How many bones in a human Skeleton?– 206
How many in babies?~ 300
What are bones?– A solid network of living cells
and protein fibers that are surrounded by deposits of calcium salts
Bones: 3 PartsSpongy bone–Not soft or spongy–Very strong–Structure
resembles the supporting structure of bridges.
–Strong but lightweight
Compact bone:–Very dense (no
spaces like spongy bone)
– Outer portion of bone
–Contains Haversian canal for veins and arteries to run through
Haversian Canals
Bone Marrow:–Soft tissue–Found in bone cavities–Yellow Marrow: fat cells–Red marrow:
makes red blood cells, platelets and most white blood cells~1/2 red marrow turns into yellow in adultsIf severe blood loss, some yellow can turn back to red
Development of bone:
Cartilage: Tough, elastic, connective tissue– Found in: ears, between bones, larynx,
and other various places.
Development of Bonehttp://www.youtube.com/watch?v=78RBpWSOl08
Ossification: cartilage replaced by bone
– Osteoblasts:cells that build bone
– Osteoclasts:cells that break down bone– growth Plates: found in most long bones
(leg and arm bones) cartilage continues to grow here until completely replaced by bone during adolescence
Types of Joints
Ball and socket
Types of Joints
Hinge
Types of Joints
Saddle
Types of Joints
Pivot
Structure of Joints
Ligaments: Connect Bone to Bone
Anterior Cruciate Ligament
Structure of Joints
Bursa:
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Types of Muscle
The human body is comprised of 324 muscles Muscle makes up 30-35% (in women) and 42-47%
(in men) of body mass.
Three types of muscle:
Skeletal muscle
Smooth muscle
Cardiac muscle
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A. Skeletal (Striated) Muscle Connects the various parts of the skeleton through one or more
connective tissue tendons During muscle contraction, skeletal muscle shortens and moves
various parts of the skeleton Activated through signals carried to the muscles via nerves
voluntary control Repeated activation of a skeletal muscle can lead to fatigue Can have many nuclei
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Skeletal Muscles work in PAIRSBending or straightening of elbow
requires the coordinated interplay of the biceps and triceps muscles
B. Smooth Muscle
Located in the blood vessels, the
respiratory tract, the iris of the eye, the
gastro-intestinal tract
The contractions are slow and uniform
Is fatigue resistant
Activation is involuntary
Has one nucleus
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C. Cardiac Muscle
Has characteristics of both skeletal and smooth
muscle
Functions to provide the contractile activity of
the heart
Is very fatigue resistant
Activation of cardiac muscle is involuntary
(like smooth muscle)
Can have 2 nuclei, usually has 1
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myofibril muscle fiber muscle fiber bundle
Components of skeletal muscle
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Muscle Fibers Cylinder-shaped cells that make up skeletal muscle
Each myofibril is made up of a number of myofilaments
Diameter of fiber (0.05-0.10 mm) Length of fiber (appr. 15 cm)
Each fiber contains contractile machinery and cell organelles
Group of fiber activated via same nerve: motor unit
Each fiber has capillaries that supply nutrients and eliminate
waste
Divided into functional units called sarcomeres
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High microscope magnification of sarcomeres
within a myofibril
Muscle Contraction
Organized in series (attached end to end)
Two types of protein myofilaments:
- Actin: thin filament - Myosin: thick filament
Projecting from each myosin are tiny contractile myosin bridges
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Muscle Contraction During muscle contraction the
myofilaments myosin and actin slide toward each other and overlap. This shortens the sacromere and the entire muscle. Muscle cells are "shocked" by nerve impulses from motor neurons.
Muscle ContractionThe filaments slide together because myosin attaches to actin
and pulls on it. Myosin head (H) attaches to actin filament (A), forming a cross bridge.
After the cross bridge is formed the myosin head bends, pulling on the actin filaments and causing them to slide:
Muscle contraction is a little like climbing a rope. The cross bridge cycle is: grab -> pull -> release, repeated over and over
(a) At rest b) Contraction
Tendons
Connect Muscle to Bone
Tendon Ruptures