• The musculoskeletal system is the organ system
that gives us the ability to move (locomotion).
The primary functions of this system include:
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.
The bones of the skull protect the brain.
Ribs and sternum (breast bone) protect the lungs and
Vertebrae protect the spinal cord.
Skeletal muscles use the bones as levers to move the
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.
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:
▫ Cartilage, Ligaments, Tendons
Anatomy and Physiology
▫ Skeletal, smooth, and cardiac
▫ The junction between two or more bones
▫ Cord-like structures that attach muscles to the
periosteum of the bone
▫ Attachments of the muscle
Origin and insertion
Anatomy and Physiology
▫ Fibrous tissue connecting two adjacent, freely
▫ Firm, dense type of connective tissue
▫ Small sac filled with synovial fluid
▫ Reduces friction between areas
Copyright 2010, John
Wiley & Sons, Inc.
• Points where bones meet
▫ Structurally: by their anatomy
Fibrous, cartilaginous, or synovial
▫ Functionally: by the degree of movement they
Immovable, slightly movable, and freely movable
• Based on what is between bones:
▫ Space (or not)
▫ Type of connective tissue present
▫ Fibrous joints - no cavity, just dense irregular
▫ Cartilaginous joints - no cavity, bones held
together by cartilage
▫ Synovial joints - have synovial cavity, dense
irregular tissue of articular capsule, and often
• Based on degree of movement they permit
▫ Synarthrosis: immovable
Pelvis, sutures, teeth
▫ Amphiarthrosis: slightly movable
Epiphyseal plate, tibia-fibula, vertebrae, pelvic
▫ Diarthrosis: freely movable
Most joints of the body
All diarthrotic joints are synovial
• Suture (synarthrosis)
▫ Joined by thin layer of dense fibrous connective
▫ Example: between bones of skull
▫ Greater distance between bones and greater amount
of dense irregular connective tissue
Distal tibia to distal fibula (amphiarthrosis)
Gomphosis (synarthrosis): tooth root in socket
(alveolar process) of mandible or maxilla
• Interosseous membrane (amphiarthrosis)
▫ Has greater amount of dense irregular connective
▫ Examples: extensive membranes between shafts
of some long bones
• Synchondrosis (synarthrosis)
▫ Cartilage connects two areas of bone
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
Most complex joints
Allow a large degree of relative motion between
Surrounded by a fibrous capsule (synovial capsule)
Hip, knee, elbow, ankle, etc.
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
• In some cases synovial joints include:
▫ Ligaments (either inside or outside of joint cavity)
▫ Menisci (cartilage discs)
▫ Articular fat pads
Sacs made of synovial membranes containing fluid
Located where friction can occur
Examples: between skin-bone, tendons-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
Movement be restricted by the presence of adipose tissue
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
Movement may be restricted if a joint has not been used for an
Cartilage: Connective tissue
•Chondroblasts lay down the
•become chondrocytes when
surrounded by extra cellular
•Chondrocytes do not mitose
•On aging, cartilage becomes
• Bone classification
There 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
These bones are involved in protection, support, and
carrying other body parts.
B. Appendicular skeleton
Bones of upper & lower limbs and the girdles (shoulder
bones and hip bones) that attach them to the axial
• Basic Bone Structure
• Bones are organs composed of hard living tissue providing structural support to the
• 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
▫ Bone tissue (osseous tissue).
▫ Fibrous connective tissue.
▫ Vascular tissue.
▫ Lymphatic tissue.
▫ Adipose tissue.
▫ Nervous tissue.
Internal Organization of a Typical Bone
Osteon = Functional unit of bone
Types of Osseous Tissue
1. Compact Bone
1. Dense, found in the walls, or cortex
2. Spongy or Cancellous Bone
1. Network of struts and thin plates (trabeculae)
1. Red and Yellow
1. Compact Bone
• Osteon = functional unit of
• The mineral matrix is
• Osteoblasts lay down the
matrix in layers (lamellae)
▫ Become osteocytes when
surrounded by EC matrix
• Osteoclasts break
2. Spongy Bone
• No osteons
• Lacy network of
• Covered by
• Red Marrow
▫ Blood Precursors
• Yellow Marrow
▫ Mostly fat
• 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
It consists of a delicate mesh of reticular tissue saturated
with immature red blood cells and scattered adipocytes.
• 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.
• 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
Synthesize and secrete collagen fibers and other organic components of
Initiate the process of calcification.
Found in both the periosteum and the endosteum
The blue arrows indicate the
osteoblasts. The yellow arrows indicate
the bone matrix they’ve just secreted.
Mature bone cells.
Osteoblasts that have become trapped by the secretion of
No longer secrete matrix.
Responsible for maintaining the bone tissue.
▫ 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.
• 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:
• 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
▫ Bone also contains smaller amounts of magnesium,
▫ fluoride, and sodium.
▫ These minerals give bone its characteristic hardness and the
ability to resist compression.
• 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
▫ Joint surface of each epiphysis is covered with a type of
hyaline cartilage known as articular cartilage.
• 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
These enter the bone of the shaft via a nutrient foramen.
▫ Periosteum is connected to the bone matrix via strong strands of
• Internal bone surfaces are covered with a delicate
connective tissue membrane known as the
▫ Covers the spongy bone in the marrow cavities and
lines the canals that pass through compact bone.
▫ Contains both osteoblasts and osteoclasts.
• 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
• 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-
▫ Plates of Bone e.g. skull
▫ The replacement of hyaline cartilage with bone is known as endo-
• Long Bones