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Introduction to Muscloskeletal system

Dr.AMMAR JAWADMBChB, MPH

Musculoskeletal System

•The musculoskeletal system is the organ system that gives us the ability to move (locomotion). The primary functions of this system include:

Skeletal System

Functions:1. Support

The bones of the legs, pelvic, and vertebral column support the weight of the erect body.

The mandible (jawbone) supports the teeth. Other bones support various organs and tissues.

2. Protection The bones of the skull protect the brain. Ribs and sternum (breast bone) protect the lungs and

heart. Vertebrae protect the spinal cord.

Skeletal System

3. Movement Skeletal muscles use the bones as levers to move the

body.

4. Reservoir for minerals and adipose tissue 99% of the body’s calcium is stored in bone. 85% of the body’s phosphorous is stored in bone.

5. Hematopoiesis All blood cells are made in the marrow of certain bones.

6. Triglyceride Storage Yellow bone marrow

Triglycerides stored in adipose cells Serves as a potential chemical energy reserve

•7. Heat generation

•The musculoskeletal system is comprised up of the following tissues:▫Muscles▫Bones▫Cartilage, Ligaments, Tendons▫Joints

Muscles

Anatomy and Physiology•Muscles

▫ Skeletal, smooth, and cardiac •Joints

▫ The junction between two or more bones •Tendons

▫ Cord-like structures that attach muscles to the periosteum of the bone

▫ Attachments of the muscle Origin and insertion

Anatomy and Physiology•Ligaments

▫Fibrous tissue connecting two adjacent, freely movable bones

•Cartilage▫Firm, dense type of connective tissue

•Bursae▫Small sac filled with synovial fluid▫Reduces friction between areas

Musculoskeletal System

•Ligaments connect bone-to-bone or reinforce joints--they are made up of tendinous tissue as well

•E.g. knee ligaments

Ligaments

Tendons• Tendons are calble-like fibrous tissues that connect

muscle-to-bone, functioning simply to transmit forces

Joints

Copyright 2010, John Wiley & Sons, Inc.

Joints

•Points where bones meet•Classifications

▫ Structurally: by their anatomy Fibrous, cartilaginous, or synovial

▫ Functionally: by the degree of movement they permit Immovable, slightly movable, and freely

movable

Structural Classification•Based on what is between bones:

▫ Space (or not)▫ Type of connective tissue present

•Types▫ Fibrous joints - no cavity, just dense

irregular connective tissue▫ Cartilaginous joints - no cavity, bones held

together by cartilage▫ Synovial joints - have synovial cavity,

dense irregular tissue of articular capsule, and often ligaments

Functional Classification•Based on degree of movement they permit•Types

▫Synarthrosis: immovable Pelvis, sutures, teeth

▫Amphiarthrosis: slightly movable Epiphyseal plate, tibia-fibula, vertebrae,

pelvic symphysis▫Diarthrosis: freely movable

Most joints of the body All diarthrotic joints are synovial

Fibrous Joints• Suture (synarthrosis)

▫ Joined by thin layer of dense fibrous connective tissue

▫Example: between bones of skull• Syndesmosis

▫Greater distance between bones and greater amount of dense irregular connective tissue

▫Examples Distal tibia to distal fibula (amphiarthrosis) Gomphosis (synarthrosis): tooth root in socket

(alveolar process) of mandible or maxilla

Fibrous Joints•Interosseous membrane (amphiarthrosis)

▫Has greater amount of dense irregular connective tissue

▫Examples: extensive membranes between shafts of some long bones

Radius-ulna Tibia-fibula

Fibrous Joints

Fibrous Joints

Fibrous Joints

Cartilaginous Joints

• Synchondrosis (synarthrosis)▫ Cartilage connects two areas of bone▫ Example

Epiphyseal (growth) plate connecting epiphysis and diaphysis of long bone (synarthrosis)

• Symphysis (amphiarthrosos)▫ Cartilage connects two bones, but a broad disc of

fibrocartilage is present also▫ Examples: pubic symphysis and intervertebral discs

Copyright 2010, John Wiley & Sons, Inc.Cartilaginous Joints

Cartilaginous Joints

▫Synovial Most complex joints Allow a large degree of relative motion

between articulating bones Surrounded by a fibrous capsule (synovial

capsule) Hip, knee, elbow, ankle, etc.

Musculoskeletal System

Synovial fluid: The joint capsule secretes whitish fluid

that works like oil in a machine, lubricating the joint surfaces to reduce friction to promote smooth operation and extend joint life.

Synovial Joints: Structure•Synovial cavity: space containing fluid•Articular cartilage

▫Covers ends of bones, absorbs shock•Articular capsule

▫Inner layer: synovial membrane that secretes synovial fluid (reduces friction, supplies nutrients)

▫Outer layer: dense, irregular connective tissue

Synovial Joints: Structure•In some cases synovial joints include:

▫Ligaments (either inside or outside of joint cavity)

▫Menisci (cartilage discs)▫Articular fat pads▫Bursae

Sacs made of synovial membranes containing fluid

Located where friction can occur Examples: between skin-bone, tendons-

bones, muscles-bones, ligaments-bones

Copyright 2010, John Wiley & Sons, Inc.Synovial Joints: Structure

Copyright 2010, John Wiley & Sons, Inc.Knee Joint

Joints (Factors Affecting Contact and Range for Motion at Synovial Joints)

•Range of motion (ROM)▫Refers to the range, measured in degrees of a

circle, through which the bones of a joint can be moved

•Factors contribute to keeping the articular surfaces in contact and affect range of motion:▫Structure or shape of the articulating

bones Shape of bones determines how closely they fit

together

▫Strength and tension of the joint ligaments Ligaments are tense when the joint is in certain

positions Tense ligaments restrict the range of motion

Joints (Factors Affecting Contact and Range for Motion at Synovial Joints)

▫Arrangement and tension of the muscles Muscle tension reinforces the restraint placed on a

joint by its ligaments , and thus restricts movement▫Contact of soft parts

The point at which one body surface contacts another may limit mobility

Movement be restricted by the presence of adipose tissue

▫Hormones Flexibility may also be affected by hormones Relaxin increases the flexibility of the pubic symphysis

and loosens the ligaments between the sacrum and hip bone toward the end of pregnancy

▫Disuse Movement may be restricted if a joint has not been

used for an extended period

Bone and cartilage

Cartilage: Connective tissue

•Chondroblasts lay down the matrix,

• become chondrocytes when surrounded by extra cellular matrix

•Chondrocytes do not mitose• Poor healing

•On aging, cartilage becomes calcified

• Less flexible• Not bone

Elastic: More flexible, e.g., ear

•Hyaline▫usually in the joints

FibrocartilageResists compression—IV Disk, menisci

Types (shapes) of Bones

•Long▫Femur

•Short▫Carpal

•Sesamoid▫Patella

•Flat▫Scapula

•Irregular▫Vertebra

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Bone

•Bone classificationThere are 206 bones in the human body.•Skeleton system classified into two groups:

A. Axial skeleton Forms long axis of the body. Includes the bones of the skull, vertebral column, and rib

cage. These bones are involved in protection, support, and

carrying other body parts.

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Skeletal System

B. Appendicular skeleton Bones of upper & lower limbs and the girdles (shoulder

bones and hip bones) that attach them to the axial skeleton.

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Skeletal System• Basic Bone Structure• Bones are organs composed of hard living tissue providing structural support to the

body. • It is a hard matrix of calcium salts deposited around protein fibers. Minerals make

bone rigid and proteins (collagen) provide strength and elasticity.Bones are organs. Thus, they’re composed of multiple tissue types. Bones are composed of:▫ Bone tissue (osseous tissue).

▫ Fibrous connective tissue.

▫ Cartilage.

▫ Vascular tissue.

▫ Lymphatic tissue.

▫ Adipose tissue.

▫ Nervous tissue.

Typical (Long) Bone Structure

Internal Organization of a Typical Bone

Osteon = Functional unit of bone

Types of Osseous Tissue1. Compact Bone

1. Dense, found in the walls, or cortex2. Spongy or Cancellous Bone

1. Network of struts and thin plates (trabeculae)

3. Marrow1. Red and Yellow

1. Compact Bone

• Osteon = functional unit of bone

• The mineral matrix is hydroxyapatite

• Osteoblasts lay down the matrix in layers (lamellae)▫ Become osteocytes when

surrounded by EC matrix▫ Lacunae

•Osteoclasts break down bone

2. Spongy Bone•No osteons•Lacy network of

struts called trabeculae reinforce the bone

•Covered by endosteum

3. Marrow•Red Marrow

▫Active▫Blood Precursors

•Yellow Marrow▫ Inactive▫Mostly fat

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Skeletal System

•Bone marrow is a general term for the soft tissue occupying the medullary cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger haversian canals.

Red bone marrow looks like blood but with a thicker consistency.

It consists of a delicate mesh of reticular tissue saturated with immature red blood cells and scattered adipocytes.

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Skeletal System

Bone Marrow

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Skeletal System

•In a child, the medullary cavity of nearly every bone is filled with red bone marrow.

•In young to middle-aged adults, the long bones are filled with fatty yellow bone marrow.▫Yellow marrow no longer produces blood, although in

the event of severe or chronic anemia, it can transform back into red marrow

•In adults, red marrow is limited to the axial skeleton, pelvic girdle, and proximal heads of the humerus and the femur.

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Skeletal System

•Bone tissue is a type of connective tissue consist of cells and a big amount of extra-cellular matrix.

•Bone cells:

•Osteogenic cells▫Undergo cell division; the resulting cells

develop into osteoblasts

OsteoblastsBone-building cells.Synthesize and secrete collagen fibers and other organic components of bone matrix. Initiate the process of calcification.Found in both the periosteum and the endosteum

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The blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.

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Skeletal System

Osteocytes Mature bone cells. Osteoblasts that have become trapped by the secretion of

matrix. No longer secrete matrix. Responsible for maintaining the bone tissue.

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Skeletal System

Osteoclasts▫Huge cells derived from the fusion of as many as 50

monocytes (a type of white blood cell).▫Cells that digest bone matrix – this process is called

bone resorption and is part of normal bone growth, development, maintenance, and repair.

▫Concentrated in the endosteum.

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Skeletal System

•Bone Matrix:▫Consists of organic and inorganic components.▫1/3 organic and 2/3 inorganic by weight▫Organic component consists of several materials that

are secreted by the osteoblasts:

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Skeletal System

• Inorganic component of bone matrix▫ Consists mainly of two components : 1. Calcium phosphate.2. Calcium hydroxide. ▫ These 2 salts interact to form a compound called

hydroxyapatite.▫ Bone also contains smaller amounts of magnesium, ▫ fluoride, and sodium.▫ These minerals give bone its characteristic hardness and the

ability to resist compression.

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Skeletal System

•Long Bone Structure•Shaft plus 2 expanded ends.•Shaft is known as the diaphysis.

▫ Consists of a thick collar of compact bone surrounding a central marrow cavity

•Expanded ends are epiphyses▫ Thin layer of compact bone covering an interior of spongy

bone.▫ Joint surface of each epiphysis is covered with a type of

hyaline cartilage known as articular cartilage.

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Skeletal System

• The external surface of the entire bone except for the joint surfaces of the epiphyses is covered by a double-layered membrane known as the periosteum.▫ Periosteum is richly supplied with nerve fibers, lymphatic vessels and

blood vessels. These enter the bone of the shaft via a nutrient foramen.

▫ Periosteum is connected to the bone matrix via strong strands of collagen

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Skeletal System

• Internal bone surfaces are covered with a delicate connective tissue membrane known as the endosteum.▫Covers the spongy bone in the marrow cavities and

lines the canals that pass through compact bone.▫Contains both osteoblasts and osteoclasts.

Bone Development

• Osteogenesis (ossification): is the process of bone tissue formation.

• In embryos this leads to the formation of the bony skeleton.

• In children and young adults, ossification occurs as part of bone growth.

• In adults, it occurs as part of bone re-modeling and bone repair.

Formation of the Bony Skeleton

• Before week 8, the human embryonic skeleton is made of fibrous membranes and hyaline cartilage.

• After week 8, bone tissue begins to replace the fibrous membranes and hyaline cartilage.▫ The development of bone from a fibrous membrane is called intra-

membranous ossification.▫ Plates of Bone e.g. skull

▫ The replacement of hyaline cartilage with bone is known as endo-chondral ossification.

• Long Bones

Bone Circulation