The Skeletal System

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

The Skeletal System Parts of the skeletal system

Bones (skeleton) Joints Cartilages Ligaments

Two subdivisions of the skeleton Axial skeleton Appendicular skeleton


Functions 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

Figure 5.2b


Classification of Bones on the Basis of Shape

Figure 5.1


Classification of Bones Long bones

Typically longer than they are wide Have a shaft with heads at both ends Contain mostly compact bone Example:

Femur Humerus


Classification of Bones

Figure 5.1a


Classification of Bones Short bones

Generally cube-shape Contain mostly spongy bone Example:

Carpals Tarsals



Figure 5.1b


Classification of Bones Flat bones

Thin, flattened, and usually curved Two thin layers of compact bone surround a

layer of spongy bone Example:

Skull Ribs Sternum



Figure 5.1c


Classification of Bones Irregular bones

Irregular shape Do not fit into other bone classification

categories Example:

Vertebrae Hip bones



Figure 5.1d


Anatomy of a Long Bone Diaphysis

Shaft Composed of compact bone

Epiphysis Ends of the bone Composed mostly of spongy bone


Anatomy of a Long Bone

Figure 5.2a


Anatomy of a Long Bone Periosteum

Outside covering of the diaphysis Fibrous connective tissue membrane

Sharpey’s fibers Secure periosteum to underlying bone

Arteries Supply bone cells with nutrients



Figure 5.2c


Anatomy of a Long Bone Articular cartilage

Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces


Anatomy of a Long Bone Epiphyseal plate

Flat plate of hyaline cartilage seen in young, growing bone

Epiphyseal line Remnant of the epiphyseal plate Seen in adult bones



Figure 5.2a


Anatomy of a Long Bone Medullary cavity

Cavity inside of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell formation)

in infants



Figure 5.2a


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


Formation of the Human Skeleton The process of bone formation is called

ossification. 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


Types of Bone Cells Osteocytes—mature bone cells Osteoblasts—bone-forming cells Osteoclasts—bone-destroying cells

Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone

Bone remodeling is performed by both osteoblasts and osteoclasts


Bone Fractures Fracture—break in a bone Types of bone fractures

Closed (simple) fracture—break that does not penetrate the skin

Open (compound) fracture—broken bone penetrates through the skin

Bone fractures are treated by reduction and immobilization


Types of Fractures Comminuted – breaks into many fragments.

Common in aged brittle bones Compression – bone is crushed.

Common in porous bones (ex) osteoporosis Depressed – broken portion is pressed inward

Typical of skull fractures


Types of Fractures Impacted – broken ends are forced into each other

Commonly occurs when one falls and attempts to break the fall with outstretched arms.

Spiral – ragged, occurs when excessive twisting forces cause break

Common with sports fractures. Greenstick – incompletely breaks, like a green twig

breaking Common in children because they have more

collagen in their matrix and are more flexible d


Common Types of Fractures

Table 5.2


Repair of Bone Fractures1. Hematoma (blood-filled swelling) is formed2. Break is splinted by fibrocartilage to form a

callus3. Fibrocartilage callus is replaced by a bony callus4. Bony callus is remodeled to form a permanent

patch


Stages in the Healing of a Bone Fracture

Figure 5.5

HematomaExternalcallus

Bonycallus ofspongybone

Healedfracture

Newbloodvessels

Internalcallus(fibroustissue andcartilage)

Spongybonetrabecula

Hematomaformation

Fibrocartilagecallus formation

Bony callusformation

Bone remodeling



Figure 5.5, step 1

Hematoma

Hematomaformation



Figure 5.5, step 2


Newbloodvessels


Spongybonetrabecula

Hematomaformation




Figure 5.5, step 3



Newbloodvessels


Spongybonetrabecula

Hematomaformation





Figure 5.5, step 4



Healedfracture

Newbloodvessels


Spongybonetrabecula

Hematomaformation



Bone remodeling


The Axial Skeleton Forms the longitudinal axis of the body Divided into three parts

Skull Vertebral column Bony thorax


The Axial Skeleton

Figure 5.6a


The Axial Skeleton

Figure 5.6b


The Skull Two sets of bones

Cranium Facial bones

Bones are joined by sutures Only the mandible is attached by a freely movable

joint


Human Skull, Lateral View

Figure 5.7


Eight bones of the Cranium Frontal - forehead Parietal (paired) – top of the skull Temporal (paired) - temples Occipital – back of skull Sphenoid – forms floor of cranial cavity Ethmoid – forms roof of nasal cavity


Human Skull, Superior View

Figure 5.8


Human Skull, Inferior View

Figure 5.9


Human Skull, Anterior View

Figure 5.11


Fourteen Facial Bones Maxillae – upper jaw Mandible – lower jaw Palatine (paired) – Zygomatic(paired) – cheekbones Lacrimal (paired) – inside of eye, outside of nose Nasal (paired) – bridge of noes Vomer (paired) – median line of nasal cavity, means

“plow” Inferior Conchae (paired) – curved bones projecting

from the side walls


The Hyoid Bone

Figure 5.12


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


The Vertebral Column Each vertebrae is given a name according to its

location There are 24 single vertebral bones separated

by intervertebral discs 7 cervical vertebrae are in the neck 12 thoracic vertebrae are in the chest

region 5 lumbar vertebrae are associated with the

lower back


The Vertebral Column Nine vertebrae fuse to form two composite bones

Sacrum (5) Coccyx (4)


The Vertebral Column

Figure 5.14


The Vertebral Column 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 Develop after birth



Figure 5.15



Figure 5.16


A Typical Vertebrae, Superior View

Figure 5.17


Regional Characteristics of Vertebrae

Figure 5.18a



Figure 5.18b



Figure 5.18c



Figure 5.18d


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 vertebrates have


Sacrum and Coccyx

Figure 5.19


The Bony Thorax Forms a cage to protect major organs Consists of three parts

Sternum Ribs

True ribs (pairs 1–7), attach directly to sternum False ribs (pairs 8–12), attach indirectly to

sternum Floating ribs (pairs 11–12), don’t attach at all

Thoracic vertebrae


The Bony Thorax

Figure 5.20a


The Appendicular Skeleton Composed of 126 bones

Limbs (appendages) Pectoral girdle Pelvic girdle


The Appendicular Skeleton

Figure 5.6a


The Appendicular Skeleton

Figure 5.6b


Bones of the Pelvic Girdle Formed by two coxal (ossa coxae) bones Composed of three pairs of fused bones

Ilium Ischium Pubis


Bones of the Pelvic Girdle The total weight of the upper body rests on the

pelvis It protects several organs

Reproductive organs Urinary bladder Part of the large intestine


The Pelvis

Figure 5.24a


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


Gender Differences of the Pelvis

Figure 5.24c


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 Diarthroses

Freely moveable joints


Structural Classification of Joints Fibrous joints

Generally immovable Cartilaginous joints

Immovable or slightly moveable Synovial joints

Freely moveable


Summary of Joint Classes[Insert Table 5.3 here]

Table 5.3


Fibrous Joints Bones united by fibrous tissue Example:

Sutures


Fibrous Joints

Figure 5.28a–b


Cartilaginous Joints Bones connected by cartilage Example:

Pubic symphysis Intervertebral joints


Cartilaginous Joints

Figure 5.28c–e


Synovial Joints Articulating bones are separated by a joint cavity Synovial fluid is found in the joint cavity


Synovial Joints

Figure 5.28f–h


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


Types of Synovial Joints

Figure 5.30a–c


Types of Synovial Joints

Figure 5.30d–f


Types of JointsHinge- A hinge joint allows extension and retraction

of an appendage. (Elbow, Knee)


Ball and Socket- A ball and socket joint allows for radial movement in almost any direction. They are found in the hips and shoulders. (Hip, Shoulder)


Gliding- In a gliding or plane joint bones slide past each other. Mid-carpal and mid-tarsal joints are gliding joints. (Hands, Feet)


Saddle- This type of joint occurs when the touching surfaces of two bones have both concave and convex regions with the shapes of the two bones complementing one other and allowing a wide range of movement. (Thumb)


6 Types of Synovial Joints Plane – ex. Carpals Hinge – ex. Humerus Pivot – ex. Ulna and Radius Condyloid – ex. Metacarpal and phalanges Saddle – ex. Carpal and metacarpal Ball and socket – ex humerus and scapula


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

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


Arthritis





Bursitis Inflammation of the Bursa (fluid filled sac

surrounding the joint). A bursa can become inflamed from injury,

infection (rare in the shoulder), or due to an underlying rheumatic condition.

Bursitis is typically identified by localized pain or swelling, tenderness, and pain with motion of the tissues in the affected area.




Tendonitis Sometimes the tendons become

inflamed for a variety of reasons, and the action of pulling the muscle becomes irritating. If the normal smooth gliding motion of your tendon is impaired, the tendon will become inflamed and movement will become painful. This is called tendonitis, and literally means inflammation of the tendon.

The most common cause of tendonitis is overuse.



Skeletal Changes Throughout Life

Figure 5.16


Scoliosis Scoliosis is an abnormal curvature

of the spine. If your child has scoliosis, the view from behind may reveal one or more abnormal curves.Scoliosis runs in families, but doctors often don't know the cause. More girls than boys have severe scoliosis. Adult scoliosis may be a worsening of a condition that began in childhood, but wasn't diagnosed or treated. In other cases, scoliosis may result from a degenerative joint condition in the spine.






Kyphosis With kyphosis, your spine may look

normal or you may develop a hump. Kyphosis can occur as a result of developmental problems; degenerative diseases, such as arthritis of the spine; osteoporosis with compression fractures of the vertebrae; or trauma to the spine. It can affect children, adolescents and adults.




Lordosis A normal spine, when viewed from behind

appears straight. However, a spine affected by lordosis shows evidence of a curvature of the back bones (vertebrae) in the lower back area, giving the child a "swayback" appearance.




Skeletal Changes Throughout Life Osteoporosis

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 (also known as dowager’s hump)

Estrogen aids in health and normal density of a female skeleton


Osteoporosis Osteoporosis is a term that means

"porous bones." It is a skeletal disease affecting women and men. Osteoporosis is a condition in which bones have lost mineralse specially calcium ﾑmaking them weaker, more brittle, and susceptible to fractures (broken bones). Any bone in the body can be affected by osteoporosis, but the most common places where fractures occur are the back (spine), hips, and wrists.



Figure 5.34






Figure 5.35

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The Skeletal System