muscoskeletal system

Axial Skeleton

The part of the skeleton that includes the skull, vertebral column, and rib cage.

Appendicular Skeleton

The part of the skeleton that includes the limbs and girdles (shoulder and pelvic girdles).

Primary ossification center

The first location in a developing bone where ossification (bone formation) occurs.

Secondary ossification center

Locations in bones where ossification occurs after the primary center, usually in the epiphyses.

function of the skeleton

• Protection: Encloses internal organs 

• CNS, Cardio, Resp, Repro... 

• Support: Rigid structural framework 

• Movement: Anchors skeletal muscle 

• Mineral Storage: homeostasis 

• Blood cell production: Red bone marrow 

• Fat (energy storage): Yellow bone marrow 

Blood Cell production and energy storage as a

function of the skeleton

• Bone Marrow is a dynamic semi-solid tissue found within bone

• Red Marrow: high number of haematopoietic stem cells (blood cell formation)

• Erythrocytes, monocytes, neutrophils, etc

• Located in spongy/trabecular bone, in ends of bones or flat bones

 

• Yellow Marrow: high number of adipocytes (fat cells) for energy/fat storage

           > Located in medullary cavity of long bones

Collagen fibers

Organic substances produced by the body that provide strength and flexibility in bone.

bone types

• Describes bone shape and not length

• Long bones in arms or legs

• Short bones mainly in wrist and hands or ankle

• Skull bones and ribs/sternum are flat

• Sesamoid bones form from within tendon, eg is patella

• Irregular is vertebra

 

Long bones

Bones that are longer than they are wide, such as those found in the arms and legs.

Short bones

Bones that are approximately equal in length and width, such as those in the wrist and ankle.

Irregular bones

Bones that have complex shapes, such as vertebrae.

Cortical bone

Also known as compact bone, it's the dense outer layer of bone.

Prominent composition/type in diaphysis (shaft of long bone)

• Contains Osteons (how bone is built)

     > Main unit of compact bone microstructure

• Strength in uniform direction due to being compact

Trabecular bone

Also known as spongy bone, it's characterized by a lattice-like structure.

Prominent composition/type in heads of long bone & other bone structures (flat, irregular, etc)

 • Contains Trabeculae (bony struts)

• Strength in multiple directions bc of latticework and space In/ around it, has red bone marrow which is essential for the making of blood cells (haematopoiesis)

gross anatomy of the long bone

bone as a suppourtive connective tissue/ its composition

Bone extracellular matrix

=

Osteons

The structural unit of compact bone, consisting of a central Haversian canal surrounded by concentric lamellae.

Haversian canal

Central canal in an osteon that contains blood vessels and nerves.

Lacunae

Small cavities in bone tissue that contain osteocytes.

Osteoclast

Bone-resorbing cell responsible for breaking down bone tissue.

Osteoblast

Osteocyte

Mature bone cell that maintains the bone matrix and communicates via canaliculi.

osteoprogenitor cells

 

osteon components

Osteon Components (A.K.A. Haversian System) from compact bone

Trabeculae

Structural units of spongy bone, consisting of thin struts that create a web-like matrix.

Trabeculae is found in spongey/ trabecular bone, in the heads of bones

• Each Trabeculae contains:

• Lamella (layers of bone) arranged in plates or sheets

• Much like interstitial lamella

•  Lacunae & Canaliculi for osteocytes

• Trabeculae do NOT have

• Concentric lamella (layered rings of bone)

• A Haversian (central) canal as the cells can grab on the blood vessels from the surrounding area

  

bone cell nutrition

Osteoprogenitors, Osteoblasts and Osteoclasts

how do osteons forms

Osteons are created during the process of bone formation and maintained or updated during the bone remodelling process

1. 

function of cartilage tissue

• Maintains shape

• Resist compression & absorbs shock

•  Provides smooth surface to minimise friction (articular cartilage in long bone does this and resists compression)

cartilage compositon and cells

types of cartilage- hyaline

Appearance: Clear, glassy, fine collage fibres

Location: Ends of long bones at moveable joints; trachea

Function: Smooth surface prevents friction (thus pain) when joint moves; holds airways open so air can pass through

fibrocartilage

Very fibrous and with lots of collagen bundles, giving it more strength and resistance, so good for areas that need to maintain integrity

elastic cartilage

• Lots of elastic fibres, giving web appearance, have some stretch and recoil back into shape

ossification

intramembranous ossification

•  Bone formation within the embryonic tissue membrane, during first two months of development (primary method of bone formation for these 2 months)

• Mainly takes place for the flat and irregular bones of the skull

 

• 

intramembranous ossification steps

Based on growth factors in area ( a signal sent in area)

endochondral ossification

Bone formation within the Cartilage (-chondral) model

 

 

interstitial vs appositional growth

interstitial growth

(inside tissue at interstitial plate)

• Bone growth in length

• Occurs ‘within bone’

• Occurs at Epiphyseal Plate

• Chondrocytes divide increasing Hyaline cartilage from the inside

• Growth of cartilage pushing epiphysis further from metaphysis

• Hyaline cartilage gradually ossifies (Adulthood)

• Epiphyseal line

s

appositional growth

 Bone growth in width,  Occurs on ‘edges of bone’

• Bony structure is formed

• Osteogenic cells within periosteum differentiated to form osteoblasts

• Osteoblasts lay down new layers of bone (lamellae) on the edges of bone

• Osteoblasts trap themselves TURN INTO osteocytes

bone remodelling

Process of bone cells removing old bone and replacing with new bone

• Osteoclasts removing bone by reabsorbing it at equal rates of Osteoblasts forming new bone (important balance)

• Balance of bone removal and bone formation = repair/maintenance

• Breaking down of the bones releases minerals into the body

• Adeq

bone fracture and repair

what are joints

Joints (a.k.a. articulations) form where two bones are interconnected

• Can also be considered the point of contact between two structures

• Where bone meets bone

•  Where cartilage meets bone

•  Where teeth meet bone

  

Classifying joints - structural and functional classifications

Functional Classifications: Refers to the range of motion at an articulation

•  Immobile (synarthrosis) = no movement

•  Partly mobile (amphiarthrosis) = little movement

•  Freely mobile (diarthrosis) = wide range of movement

 

• Structural Classifications: Refers to the components & features of the joint

• Bony = complete fusion of two bones

•  Fibrous = held together by dense collagen fibres

•  Cartilaginous = held together by cartilage

•  Synovial = contain a joint space held together by joint capsule

 

Each joint must compromise strength and stability for its range of motion

            STRUCTURE = FUNCTION

structural classification of joints- bony joints

• 

structural classification - fibrous joints

• 

• 

general features of synovial joints

Synovial joints are the most common in the human body

 

1.

the six types of synovial joints

ball and socket joints

• Multiaxial meaning that you can use multiple axes to move on multiple planes

hinge joints

• Uniaxial meaning that it uses one axes to move on one plane

• Meaning you can only go forwards and backwards so flexion and extension

• Example is the ankle,

  

plane/ gliding joints

Nonaxial or multiaxial meaning that they slide/move across all plains depending on the environment, they have no specific movement, found in the feet e.g

saddle joints

• Can do adduction, abduction, extension and flexion

• Only in few places, including thumb

• Biaxial meaning uses two axes to move on two planes

  

condylar joints

• Shallow socket

• Also biaxial

  

pivot joints

allow for rotation

how do muscles allow for movement

•  Usually the distal end

  

movement at synovial joints

 The joint must be from the moveable class for movements to occur

• 

muscles function

Motion: walking, running, moves blood around the body, urine, muscles allow our chest muscles to work and for air to come in

2. Stabilising Body Position: posture/tension on skeleton frame

3. Regulation of Organ Volumes: sphincters, oesophageal is an example, keeps acid in stomach

4. Support of Soft Tissue: shield and weight support of organs, i.e the pelvis and the chest

5. Maintain body temperature: heat through contractions/shivering of muscles to keep us warm

6. Storage nutrients: Amino acid release from skeletal muscle breakdown

Co-ordinated action of muscle groups

Skeletal muscles function in groups to move a joint

• 

3 types of muscles and characteristics

1. Skeletal Muscle: Attaches to bone- moves things at the joints

2. Cardiac Muscle: Forms the heart

3. Smooth Muscle: Located within walls of hollow organs, like blood vessels, in intestines to contract and push food through

skeletal muscle

cardiac muscle

The Muscles of the Heart

• Muscle appears ‘Striated’ in one direction

• cells have one central nucleus and are branched to connect togethor

• Involuntary Control; Autorhythmic

smooth muscle

skeletal muscle cells

Sarcoplasm (muscle cell cytoplasm) also contains:

•   Mitochondria: energy production for contraction

•   Glycogen: stored for energy for muscle

•  Myoglobin: red pigment that binds Oxygen

•  Transverse (T) tubules: invaginations of cell membrane for shuttling of chemicals throughout muscle

•  Sarcoplasmic Reticulum (smooth ER): stores and transports cellular substances

  

skeletal muscle layers

skeletal muscle contractions

• 

cardiac muscle cells

smooth muscle

 

• 

muscle regeneration