Anatomy Unit 4: Skeletal Systems

5.1 Skeletal basics

Main Functions

1. Support the body

2. Protect soft organs

3. Movement due to attached skeletal muscles

4. storage of minerals and fats

5. blood cell formation.

Skeletal system parts

• Bones (skeleton)

• Joints

• Cartilages

• Ligaments (connect bone to bone)

Divisions

• Axial skeleton

  • Forms longitudinal axis of body

  • 

• Appendicular Skeleton

  • Bones of limbs and girdles

    • 

Types of bones

• Bone: connective tissue

• 2 basic types

  • Compact bone

    • homogeneous

  • Spongy Bone

    • Small needle-like pieces of bone with many open spaces

Classification of bones by shape

• Long bones

  • Longer than wide

  • Shafts with heads at both ends

  • Contain mostly compact bone

  • Examples include: femur and humerus

• Short bones

  • Cube-shaped

  • Contain mostly spongy bone

  • Examples include: carpals, tarsals

• Flat bones

  • Thin and flattened

  • Usually curved

  • Thin layer compact bone around layer of spongy bones

  • Examples include: skull, ribs, and sternum

• Irregular bones

  • Irregular shape

  • Usually curved

  • Do not fit in any other bone shape category

  • Examples include: vertebrae, pelvis

5.2 Bone Anatomy

Gross Anatomy of long bones

• Diaphysis

  • Shaft

  • Composed of compact bone

Epiphysis

• Ends of the bone

• Composed mostly of spongy bone

Long Bones

• Periosteum

  • Outside covering of diaphysis

  • Fibrous connective tissue membrane

• Sharpey’s fibers

  • Secure periosteum to underlying bone

• Arteries

  • Supply bone cells with nutrients

• Articular Cartilage

  • Covers external surface of epiphyses

  • Made of hyaline cartilage

  • Decreases friction at joint surfaces

• Medullary cavity

  • Cavity of shaft

  • Contains yellow marrow(adults) or red marrow (infants)

Bone markings

• Surface features of bones

• Sites of attachments for muscles, tendons, and ligaments

• Passage for nerves and blood vessels

• Categories

  • Projections and processes

    • Grow out from bone surface

  • Depressions of cavities

    • Indentions

Bone anatomy (Microscopic)

• Osteon

  • A unit of compact bone

• Central (Haversian) canal

  • Opening in center of osteon

  • Carries blood vessels, nerves

• Perforating (Volkmans) canal

  • Canal perpendicular to central canal

  • Carries blood vessels, nerves

• Lacunae

  • Cavities containing bone cells (osteocytes)

  • arranged in concentric rings

• Lamellae

  • Rings around central canal

  • Sites of lacunae

• Canaliculi

  • Tiny canals

  • Radiate from central canal to lacunae

  • Form a transport system

  

Bone development: Childhood

• Embryos: skeleton is primarily hyaline cartilage

• During development, much of this cartilage replaced by bone

• Cartilage remains in isolated areas

  • Bridge of nose

  • Parts of ribs

  • Joints

• Epiphyseal plate allow for growth of long bone during childhood

• New cartilage is continuously formed

• Older cartilage becomes ossified

• Bone grows in length because

  1. Cartilage is broken down

  2. Bone replaces cartilage.

  3. Bones remodeled and lengthened until growth stops

  4. Bone change shape somewhat

  5. Bone grows in width

• Remodeling

  1. Bone resorbed in epiphyseal plate

  2. Bone added by appositional growth

  3. Bone is reabsorbed

  4. 

Remodeling

• Osteocytes

  • Mature bone cells

• Osteoblasts

  • Bone forming cells

• Osteoclasts

  • Bone-destroying cells(break down bone matrix for remodeling and release of calcium)

Bone Fractures

• A break in a bone

• Types of bone fractures

  • Closed(simple) fracture

    • does not penetrate the skin

  • Open(compound) fracture

    • broken bone penetrates through the skin

• Treated by

  • Reduction(realignment) and immobilization

  

Fracture repair

• Hematoma formation

  • Blood filled swelling is formed

• Fibrocartilage callus formation

  • Break is splinted by fibrocartilage to form a callus

• Bony callus formation

  • Fibrocartilage callus is replaced by a bony callus

• Bone remodelling

  • Bony callus is remodeled to form a permanent patch

5.3 Axial Skeleton

Axial Skeleton Overview

• Forms longitudinal part of body

• Divided into 3 parts

  • Skull

  • Vertebral column

  • Bony thorax

Skull

• Two sets of bones

  • Cranium

  • Facial bones

• Bones are joined by sutures

• Only mandible is attached by a freely movable joint

Paranasal sinuses

• Hollow portion of bones surrounding nasal cavity

• Functions to lighten the skull

Hyoid Bone

• Only bone does not articulate with another bone

• Serves as moveable base for tongue

Vertebral Column

• Vertebrae separated by intervertebral discs

• SPine has normal curvature

• Each vertebrae is given name according to location

  • 1st cervical vertebra(atlas)

  • 2nd cervical vertebra(axis)

  • Cervical curbature (C1-C7)

  • Thoracic curvature(T1-T12)

  • Lumbar curvature(L1-L5)

  • Sacrum and Coccyx

  

Bony Thorax

• Forms a cage to protect major organs

The Skull

• At birth, skull bones incomplete

• Bones joined by fibrous membranes- fontanelles

  • Allow brain to grow

  • Convert to bone within 24 months after birth

• Fontanelles are completely replaced with bone within two years after birth

Fetal skull large compared to infants total body length

5.4 Appendicular Skeleton

General Parts

• Three parts

  • Pectoral girdle

    • Two bones (per side)

      • Clavicle (collar bone)

      • Scapula(shoulder bone)

    • Allow upper limb to have exceptionally free movement

  • Pelvic girdle

  • Limbs

Bones of upper limb

• Upper arm formed by single bone: Humerus

• Forearm has two bones: Ulna and Radius

• Hand: Carpals(wrist),metacarpals(palm),phalanges(fingers)

• Pelvic gidgle

  • Hip Bones

  • Composed of three pair of fused bones

    • Ilium, Ischium, Pubic Bone

  • Total weight of upper body rests on pelvis

  • Protects several organs

    • Reproductive organs

    • urinary bladder

    • Part of large intestine

Gender Differences of the pelvis

Female

• False pelvis is wider

• Pubic arch is more than 90 degrees

• Pelvis in general is larger and rounder

Male

• Pubic arch is less than 90 degrees

• Pelvis is taller and longer

• Not meant for holding a child

Bones of lower limb

• Thi

• gh has one bone: Femur

• Lower leg has two bones

  • Tibia and Fibula

• Foot

  • Tarsus- ankle

  • Metatarsals- sole

  • Phalanges- toes

• Arches of the foot

  • Bones of the foot are arranged to form three strong arches

    • Two longitudinal

    • One transverse

5.5 Joints

General Overview

• Articulations of bones

• Functions of joints

  • Hold together bones

  • Allow for mobility

• Ways joints are classified

  • Functionally

  • Structurally

Functional classification

• Synarthroses: immovable joints

• Amphiarthrosis: slightly moveable joints

• Diarthroses: freely moveable joints

Structural classification

• Fibrous joints: generally immovable

  • Examples,

    • Sutures and syndesmoses(allow more movement than sutures)

• Cartilaginous joints: immovable or slightly moveable

  • Examples

    • Pubic symphysis

    • Intervertebral joints

• synovial joints: freely movable

  • Synovial fluid is found in joint cavity

  • Articular cartilage covers ends of boners

  • Joint surfaces enclosed by fibrous articular capsule

  • Have joint cavity filled with synovial fluid

  • Ligaments reinforce joint

  • Bursae- flattened fibrous sacs

    • Lined with synovial membranes

    • Filled with synovial fluid

    • Not actually part of the joint

  • Tendon sheath

    • Elongated bursa that wraps around tendon

Synovial Joint Types

• Plane

  • Carpals

  • Gliding movement

• Hinge joint

  • Elbows

  • Like how a door opens

• Pivot joint

  • Rotation both internal and external

  • Turning skull around

• Condyloid joint

  • Allows jaw, wrists, toes, and fingers to move up and down, from side to side, and around in circumduction.

  • Not a full rotation though!

• Saddle Joint

  • Flexion, extension, etc

  • For example, if you were throwing objects from above the head in a sport.

• Ball and socket

  • Full rotation

  • Ex. Pelvis

Inflammatory Conditions

• Bursitis- inflammation of a bursa usually caused by blow or friction

• Tendonitis- inflammation of tendon sheaths

• Arthritis- inflammatory or degenerative diseases of joints

• Osteoarthritis

• Rheumatoid arthritis

  • autoimmune disease- immune system attacks joints

  • symptoms begin with bilateral inflammation of certain joints

  • often leads to deformities

• Gouty arthritis

  • Inflammation of joints cause by deposition of urate crystals from the blood

  • can usually be controlled by diet