The Skeletal System

 Parts of the skeletal system  Bones (skeleton)—206 bones in human body  Joints  Cartilages  Ligaments  Two subdivisions of the skeleton  Axial skeleton—skull, vertebral column and thoracic cage  Appendicular skeleton—pectoral girdle, upper limbs, pelvic girdle and lower limbs

Axial Skeleton Pubic or Coxal Bone Pubis illium ischium Talus

The Skull Mandibular condyle

Axial Skeleton—Skull  Two sets of bones  Cranium  Facial bones  Bones are joined by sutures  Only the mandible is attached by a freely movable joint

The Skull

Axial Skeleton—Skull  Skull: at birth—not completely developed  Cranial bones separated by fibrous membranes called fontanels or soft spots  They allow for compression in birth canal  They are eventually replaced wit bones and become sutures.

Sinuses  Hollow portions of bones surrounding the nasal cavity  Functions of paranasal sinuses  Lighten the skull  Give resonance and amplification to voice

Hyoid bone  The only bone that does not articulate with another bone  Serves as a moveable base for the tongue  Aids in swallowing and speech

Axial Skeleton—Vertebral Column  Extends from the skull to the pelvis  Composed of vertebrae (24)  Supports the head and trunk of the body  Protects the spinal cord

 Types of vertebrae  Cervical (7)  Thoracic(12)  Lumbar(5)  Sacrum (1)  Coccyx (1) Axial Skeleton—Vertebral Column

 Supports the shoulder girdle and arms  Protects the visceral organs in chest and upper abdomen  Made of  Ribs (12 pair—2 float)  Sternum (1 long bone with 3 divisions) Axial Skeleton—Thoracic Cage

Appendicular Skeleton

Appendicular Skeleton—Pectoral Girdle  Supports arms  Made of  Clavicle (2)  Scapula (2)  Humerus  Radius  Ulna  Olecranon process (on ulna)  Hand—carpals (wrist), metacarpals (hand) and phalanges (fingers)

Appendicular Skeleton—Pelvic Girdle  2 coxal bones that come together to form the pelvis  Strong stable support for vertebral column  Attaches lower limbs to axial skeleton  Made of  Ilium  Ischium  Pubis

Gender differences of the pelvis malefemale

 Femur (thigh)  Patella (kneecap)  Tibia (lower leg-shin)  Fibula (lower leg-lateral)  Foot—tarsals (ankle), metatarsals (foot) and phalanges (toes) Calcaneus (heel bone- large tarsal) Talus-where tibia articulates with tarsals Appendicular Skeleton—Lower Limbs

Types of bones  Long Bones  Short Bones  Flat Bones  Irregular Bones

Long Bones  Parts of a long bone  Epiphysis: end of the bone that forms a joint with another bone  Epiphyseal disk: dark line at epiphysis where growth takes place  Articular cartilage: cartilage that covers the ends of bones. Serves to cushion and decrease friction

Long Bones  Diaphysis: the main shaft of the bone  Medullary Cavity: contains bone marrow, a specialized soft connective tissue Red bone marrow makes RBC’s, WBC’s and platelets Yellow bone marrow stores fat  Periosteum: tough vascular covering of the bone that functions to form and repair bone tissue

Long Bones  Compact bone: tightly packed tissue that makes up the diaphysis; very strong  Spongy bone: spongy inner portion of the bone that makes up the epiphysis; helps reduce the weight of the bone; provides strength at the ends of bones.

Bone Markings  Surface features of bones  Sites of attachments for muscles, tendons, and ligaments  Hole or opening--foramen--passages for nerves and blood vessels  Categories of bone markings  Projections or processes—grow out from the bone surface  Depressions or cavities—indentations

Microscopic Structures of Bones

Microscopic Structure of Bones  Osteocytes: mature bone cells that are arranged around canals called Haversian canals  Haversian canals hold blood vessels and nerves.  Osteocytes secrete calcium and phosphorus that form extracellular matrix that is very hard.

 Lamellae-layers of calcified matrix  Lacunae- holes in lamella where bone cells are  Canaliculus-canals so bone cells can touch each other.

Microscopic Structure of Bones  Types of bone cells  Osteoblasts: bone forming cells  Osteoclasts: bone destroying cells— break down bone for remodeling and release calcium in response to parathyroid

Formation of the Human Skeleton  In embryos, the skeleton is primarily hyaline cartilage  During development, much of this cartilage is replaced by bone  Cartilage remains in isolated areas  Bridge of the nose  Parts of ribs  Joints

Bone Growth (Ossification)  Epiphyseal plates allow for lengthwise growth of long bones during childhood  New cartilage is continuously formed  Older cartilage becomes ossified Cartilage is broken down Enclosed cartilage is digested away, opening up a medullary cavity Bone replaces cartilage through the action of osteoblasts

Bone Growth (Ossification)  Bones are remodeled and lengthened until growth stops  Bones are remodeled in response to two factors Blood calcium levels Pull of gravity and muscles on the skeleton  Bones grow in width (called appositional growth)

Long Bone Formation and Growth Figure 5.4a, step 1 Bone starting to replace cartilage In an embryo Bone collar Hyaline cartilage model (a)

Long Bone Formation and Growth Figure 5.4a, step 2 Bone starting to replace cartilage In a fetusIn an embryo Growth in bone length Blood vessels Hyaline cartilage New center of bone growth Medullary cavity Bone collar Hyaline cartilage model (a)

Long Bone Formation and Growth Figure 5.4a, step 3 Bone starting to replace cartilage Epiphyseal plate cartilage Articular cartilage Spongy bone In a childIn a fetusIn an embryo New bone forming Growth in bone width Growth in bone length Epiphyseal plate cartilage New bone forming Blood vessels Hyaline cartilage New center of bone growth Medullary cavity Bone collar Hyaline cartilage model (a)

Long Bone Formation and Growth Figure 5.4b

Joints  Junction between bones  3 Types:  Immovable—mostly fibrous  Slightly movable—mostly cartilagenous  Freely movable—synovial

Fibrous  Bones connected by fibrous material— mostly immovable  sutures

Cartilaginous Joints  Bones connected by cartilage—slightly movable  Pubic symphysis  Intervertebral joints

Synovial Joints  Articulating bones are separated by a joint cavity  Cavity is filled with Synovial fluid  Ligaments

Types of Synovial Joints  Ball and socket  Bone with ball shaped head that joins a cup shaped socket of another bone  Allows for greater range of movement of all joints  Shoulder and hip

Types of Joints  Hinge Joint  Allows movement in one plane only  Elbow and knee

Types of Joints  Pivot Joints  Allows for rotation movement  Wrist where arm and hand meet

Types of Joints  Plane or Gliding joints  Bones are nearly flat and allow for gliding and twisting movements  Bones of hand and foot

Types of Joint Movement  Flexion: bending the arm or leg  Extension: straightening the arm or leg  Hyperextension: excessive extension of the joint (owwww!)  Abduction: moving a part away from the body  Adduction: moving a part towards the body

Broken Bones  Fracture—break in a bone Fracture—break in a bone  Types of bone fractures  Closed fracture—break that does not penetrate the skin  Open fracture—broken bone penetrates through the skin  Bone fractures are treated by reduction and immobilization

Steps to healing broken bones  Hematoma (blood-filled swelling) is formed  Break is splinted by fibrocartilage to form a callus  Fibrocartilage callus is replaced by a bony callus  Bony callus is remodeled to form a permanent patch

Types of Breaks  Greenstick Fracture— incomplete fracture, only one side of the bone is broken, causes bone to bend, common in children

Types of Breaks  Hairline fracture-- incomplete fracture—it is a crack that does not break all the way through

Types of Breaks  Transverse simple fracture—complete fracture—occurs when the bone is broken into two fragments and the break is straight across

Types of Breaks  Oblique simple fracture—complete fracture—occurs when bone is broken into 2 fragments and the break is at an angle

Types of Breaks  Spiral simple fracture—complete fracture—occurs when the bone is broken into 2 fragments and the break is at an angle that is twisted

Types of Breaks  Comminuted— complete fracture—it is a break that has many fragments

Types of Breaks  Compression fracture– bone is crushed, common in skull and vertebral column