THE MUSCULOSKELETAL SYSTEM : Part 1

Structure and Function

Forms the body framework

Enables the bodyto move

Protects and supports internal organs

BonesBones

•Composed of osseous tissue

•Consists of a rich supply of blood vessels and nerves

•Osteoblasts are bone-forming cells

•Osteoclasts are responsible for reabsorbing dead bone tissue

•Osteocytes are mature bone cells

OssificationBones

The development of osteocytes and the hardening process is called ossification

calcium

phosphorusvitamin D

Ossification depends on:

Epiphyseal Plates

• “Growth Plates”

• Located on the ends of long bones

• Where osteoblasts increase bone length

• After adolescence the plates dissolve and the bone fuses, ending bone growth

Common Bone CategoriesThe adult skeleton has 206 bones.

Common Bone Categories

•Long bones(Femur)

•Short bones(Wrist bones)

•Flat bones(Skull)

•Irregular bones(Vertebrae)

•Sesamoid bones(Kneecap)

Parts of Long BonesParts of long bones:

• Diaphysis• Longest portion• Hollow shaft

• Epiphysis• Bulbous ends• Covered by cartilage

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Parts of Long Bones Part 2

•Articular cartilage: thin flexible substance that provides protection at movable points

•Medullary cavity: hollow space that contains yellow bone marrow

Parts of a Long Bone

Femur

Distal epiphysis

Diaphysis

Proximal epiphysis

Epiphyseal disksSpongy boneArticular

cartilage

Space containing red marrow

Compact bone

Medullary cavity

Yellow marrowPeriosteum

Bone Marrow: specialized flexible tissue found inside bones

Yellow Bone Marrow• Found in medullary cavity

• Major storage for fat within the body

Red Bone Marrow• Where hematopoiesis

occurs (blood cell formation)

• Found in cavities of

– Flat & short bones

– Vertebrae

– Sternum

– Ribs

– Ends of long bones9

Cranial Bones

Spinal ColumnSpinal Column

Also called:•Spine•Vertebral column•Backbone•Vertebrae

•Cervical = 7

•Thoracic = 12

•Lumbar = 5

•Sacrum = 5 fused

•Coccyx = 4 fused

**Intervertebral Discs made of fibrocartilage provide cushioning between vertebrae**

Bones of the ChestThe Thoracic Cage

•Clavicle

•Scapula

•Sternum

•Costal Cartilage

•True ribs

•False ribs

•Floating ribs

The thoracic cage surrounds the heart and lungs in the thoracic cavity.

The Pelvic Girdle

The pubic symphysis is where both coxal bones join.

Coxal Bones

Sacrum

Coccyx

Bones of the ExtremitiesBones of the Arm

Upper Arm•Humerus

Lower Arm•Ulna•Radius

Hand and Fingers•Carpals (wrist)•Metacarpals (palm)•Phalanges (fingers)

Bones of the Extremities Part 2Bones of the Leg

Upper Leg

•Femur

Lower leg

•Tibia (shin)•Fibula •Patella (kneecap)

Feet and Toes•Tarsals•Calcaneus (heel)•Metatarsals•Phalanges

Joints

Types of Joints

Amphiarthroses•Moves slightly•Ex: Pubic Symphysis

Diarthroses•Moves freely•Ex: What you tend to think of as “joints”

Synarthroses•No movement•Ex: Sutures of the skull

Tendons and LigamentsTendons are bands of fibrous tissue that connect muscles to bone

Ligaments connect bones to other bones

Movement occurs at joints with the assistance of muscles, tendons, and

ligaments

Tendons and Ligaments

MusclesMuscles

Muscles contract (shorten) and extend to provide body movement

Types of Muscles

•1. Voluntary (skeletal)

•2. Involuntary (smooth or visceral)

•3. Cardiac (heart)

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Muscles - FasciaMuscles

Most muscles are covered by a band of connective tissue called fascia, that supports the muscle

Skeletal Muscle• Attach to bones and

are responsible for body movements

• “Striated Muscle”• “Voluntary Muscle”• Muscle fiber: an

individual skeletal muscle cell

• Born with your # of muscle fibers, can only increase fiber diameter!

Smooth Muscle

• “Involuntary Muscles” or “Visceral Muscles”

• Found in the walls of many internal organs (stomach, intestines, bladder, respiratory pathways)

• Peristalsis: Wavelike contractions that move food through the digestive tract

Cardiac Muscle

• Found only in the walls of the heart

• Involuntary muscle with branching

• Intercalated discs: structures that join together many cardiac muscle cells for simultaneous contraction (heartbeat)