Lecture A

The Skeletal System

• parts of the skeletal system

  • bones (skeleton)

  • joints

  • cartilages

  • ligaments

• two subdivisions of the skeleton

  • axial skeleton

  • appendicular skeleton

Function of Bones

• support the body

• protect soft organs

• allow movement due to attached skeletal muscles

• store minerals and fats

• blood cell formation

Bones of the Human Body

• the adult skeleton has 206 bones

• two basic types of bone tissue

  • compact bone

    • homogeneous

  • spongy bone

    • small needle-like pieces of bone

    • many open spaces

Classification of Bones

• Long Bones

  • typically larger than they are wide

  • have a shaft with heads at both ends

  • contain mostly compact bone

  • examples

    • femur

    • humerus

• Short Bones

  • generally cube-shaped

  • contain mostly spongy bone

  • examples

    • carpals

    • tarsals

• Flat Bones

  • thin, flattened, and usually curved

  • two thin layers of compact bone surround a layer of spongy bone

  • examples

    • skull

    • ribs

    • sternum

• Irregular Bones

  • irregular shape

  • do not fit into other bone classification categories

  • examples

    • vertebrae

    • hip bones

Anatomy of a Long Bone

• Diaphysis

  • shaft

  • composed of compact bone

• Epiphysis

  • ends of the bone

  • composed of mostly spongy tissue

• Periosteum

  • the outside covering of the diaphysis

  • fibrous connective tissue membrane

• Sharpey’s Fibers

  • secure periosteum to underlying bone

• Arteries

  • supply bone cells with nutrients

• Articular Cartilage

  • covers the external surface of the epiphysis

  • made of hyaline cartilage

  • decreases friction at joint surfaces

• Epiphyseal Plate

  • flat plate of hyaline cartilage seen in young, growing bones

• Epiphyseal Line

  • remnant of the epiphyseal plate

  • seen in adult bones

• Medullary Cavity

  • cavity inside of the shaft

  • contains yellow marrow (mostly fat) in adults

  • contains red marrow (for blood cell formations) in infants

Bone Markings

• surface features of bones

  • sites of attachments for muscles, tendons, and ligaments

  • passages for nerves and blood vessels

• categories of bone markings

  • projections or processes - grow out from the bone surface

  • depressions or cavities - indentations

Microscopic Anatomy of Bone

• Osteon (Haversian System)

  • a unit of bone containing a central canal and matrix ring

• Central (Haversian) Canal

  • opening in the center of an osteon

  • carries blood vessels and nerves

• Perforating (Volkman’s) Canal

  • canal perpendicular to the central canal

  • carries blood vessels and nerves

• Lacunae

  • cavities containing bone cells (osteocytes)

  • arranged in concentric rings

• Lamellae

  • rings around the central canal

  • sites of lacunae

• Canaliculi

  • tiny canals

  • radiate from central canal to lacunae

  • form a transport system connecting all bone cells to a nutrient supply

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 plate allows for lengthwise growth of long bones during childhood

  • new cartilage is continuously ossified

  • enclosed cartilage is digested away, opening up a medullary cavity

  • bone replaces cartilage through the action of osteoblasts

• bones are remodeled and lengthened until growth stops

  • bones are remodeled in response to two factors

    • blood calcium levels

    • pull of gravity and muscles of the skeleton

  • bones grow in width (called appositional growth)

Types of Bone Cells

• osteocytes

  • mature bone cells

• osteoblasts

  • bone-forming cells

• osteoclasts

  • bone-destroying cells

• bone remodeling

  • performed by both osteoblasts and osteoclasts

Lecture B

Bone Fractures

• fracture - break in a bone

• types of bone fractures

  • closed (simple) fracture - break does not penetrate the skin

  • open (compound) fracture - broken bone penetrates the skin

• bone fractures are treated by reduction and immobilization

Repair of Bone Fractures

• hematoma (blood-filled swelling) is formed

• break is splinted by fibrocartilage to form a callus

• fibrocartilage callus is replaced by bony callus

• bony callus is remodeled to form a permanent patch

The Axial Skeleton

• forms the longitudinal axis of the body

• divided into three parts

  • skull - cranium and facial bones

  • vertebral column - cervical, thoracic, lumbar, and sacrum regions

  • bony thorax - ribcage and sternum

The Skull

• two sets of bones

  • cranium

  • facial bones

• bones are joined by sutures

• only the mandible is attached by a freely movable joint

Paranasal Sinuses

• hollow portions of bones surrounding the nasal cavity

• functions of paranasal sinuses

  • lighten the skull

  • give resonance and amplification

The 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

Lecture C

The Fetal Skull

• large compared to the infant’s total body length

• Fontanels - fibrous membranes connecting the cranial bones

  • allow the brain to grow

  • convert to bone within 24 months after birth

The Vertebral Column

• each vertebrae is given a name according to its location

  • there are 24 single vertebral bones separated by intervertebral discs

    • seven cervical vertebrae

      • C1 - atlas

      • C2 - axis

    • twelve thoracic vertebrae

    • five lumbar vertebrae

  • nine vertebrae form two composite bones

    • sacrum

    • coccyx

• the spine has a normal curvature

  • primary curvatures are the spinal curvatures of the thoracic and sacral regions

    • present from birth

  • secondary curvatures are the spinal curvatures of the cervical and lumbar regions

    • present after birth

  • Irregular curvatures

    • Scoliosis - left or right curvature

    • Kyphosis - hump at the top (dowagers hump)

    • Lordosis - inward curvature of the lumbar region

Sacrum and Coccyx

• Sacrum

  • formed by the fusion of five vertebrae

• Coccyx

  • formed from the fusion of three to five vertebrae

  • “tailbone” or remnant of a tail that other vertebrae have

The Bony Thorax

• forms a cage to protect major organs

• consists of three parts

  • sternum

    • manubrium - the top part

  • ribs

    • true ribs (pairs 1-7)

    • false ribs (pairs 8-12)

    • floating ribs (pairs 11-12)

  • thoracic vertebrae

Lecture D

The Appendicular Skeleton

• composed of 126 bones

  • limbs (appendages)

  • pectoral girdle

  • pelvic girdle

The Pectoral (Shoulder) Girdle

• composed of two bones

  • clavicle - collarbone

  • scapula - shoulder blade

• these bones allow the upper limb to have exceptionally free movement

Bones of the Upper Limbs

• humerus

  • forms the arm

  • single bone

• the forearm has two bones

  • ulna

    • the medial bone in anatomical position

  • radius

    • lateral bone in anatomical position

• the hand

  • carpals - wrist

  • metacarpals - palm

  • phalanges - fingers

Lecture E

Bones of the Pelvic Girdle

• formed by two coxal (ossa coxae) bones

• composed of three pairs of fused bones

  • ilium

  • ischium

  • pubis

• the total weight of the upper body rests on the pelvis

• it protects several organs

  • reproductive organs

  • urinary bladder

  • part of the large intestine

Gender Differences of the Pelvis

• the female inlet is larger and more circular

• the female pelvis as a whole is shallower, and the bones are lighter and thinner

• the female ilia flare more laterally

• the female sacrum is shorter and less curved

• the female ischial spines are shorter and farther apart; thus the outlet is larger

• the female pubic arch is more rounded because the angle of the pubic arch is greater

Bones of the Lower Limbs

• the thigh has one bone

  • femur

    • the heaviest, strongest bone in the body

• the lower leg has two bones

  • tibia

    • shinbone

    • larger and medially oriented

  • fibula

    • thin and sticklike

• the foot

  • tarsals

    • two largest tarsals

      • calcaneus (heel bone)

      • talus

  • metatarsals - sole

  • phalanges - toes

Arches of the Foot

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

  • two longitudinal

  • one transverse

Lecture F

Joints

• articulations of bones

• functions of joints

  • hold bones together

  • allow for mobility

• ways joints are classified

  • functionally

  • structurally

Functional Classification of Joints

• synarthroses

  • immovable joints

• amphiarthroses

  • slightly moveable joints

• diarthrosis

  • freely moveable joints

Structural Classification of Joint

• fibrous joints

  • generally immovable

• cartilaginous joints

  • immovable or slightly moveable

• synovial joints

  • freely moveable

Fibrous Joints

• bones united by fibrous tissue

• example

  • sutures

  • syndesmoses

    • allows more movement than sutures

    • example: the distal end of the tibia and fibula

Cartilaginous Joints

• bones connected by cartilage

• example

  • pubic symphysis

  • intervertebral joints

Synovial Joints

• articulating bones are separated by a joint cavity

• synovial fluid is found in the joint cavity

• types of synovial joints

  • plane joint

  • hinge joint

  • pivot joint

  • condyloid joint

  • saddle joint

  • ball and socket joint

Features of Synovial Joints

• articular cartilage (hyaline cartilage) covers the ends of bones

• a fibrous articular capsule encloses joint surfaces

• a joint cavity is filled with synovial fluid

• ligaments reinforce the joint

Structures Associated with the Synovial 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 a tendon

Inflammatory Conditions Associated with Joints

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

• tendonitis - inflammation of tendon sheaths

• arthritis - inflammatory or degenerative diseases of joints

  • over 100 different types

  • the most widespread crippling disease in the United States

Clinical Forms of Arthritis

• osteoarthritis

  • the most common chronic arthritis

  • probably related to normal aging processes

• rheumatoid arthritis

  • an autoimmune disease - the immune system attacks the joints

  • symptoms begin with bilateral inflammation of certain joints

  • often leads to deformities

• Gouty arthritis

  • inflammation of joints is caused by a deposition of uric acid crystals from the blood

  • can usually be controlled with diet

  • high protein diet can contribute to the production of uric acid crystals

Developmental Aspects of the Skeletal System

• at birth, the skull bones are incomplete

• bones are joined by fibrous membranes called fontanels

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

Skeletal Changes Throughout Life

• fetus

  • long bones are formed of hyaline cartilage

  • flat bones begin as fibrous membranes

  • flat and long bone models are converted to bone

• birth

  • fontanels remain until around age 2

• adolescence

  • epiphyseal plates become ossified and long bone growth ends

• size of the cranium in relationship to the body

  • 2 years old - the skull is larger in proportion to the body compared to that of an adult

  • 8 or 9 years old - the skull is near the adult size and proportion

  • between ages 6 and 11, the face grows out from the skull

• curvatures of the spine

  • primary curvatures are present at birth and are convex posteriorly

  • secondary curvatures are associated with a child’s later development and are convex anteriorly

  • abnormal spinal curvatures (scoliosis and lordosis) are often congenital

• osteoporosis (homeostatic imbalance)

  • bone-thinning disease afflicting

    • 50% of women over age 65

    • 20% of men over age 70

  • disease makes bones fragile and bones can easily fracture

  • vertebral collapse results in kyphosis

    • aka dowagers hump

  • estrogen aids in the health and normal density of a female skeleton