Ch. 7
The
Skeletal
System
Composition
• It is a solid network of active tissues
surrounded by deposits of minerals.
• Components:
–
–
–
–
Bone
Joints
Cartilage
Ligaments
Function of Bones
1. Protection- of soft tissues and organs.
2. Movement – muscles attached to bones=
function as levers.
3. Storage – of minerals (Calcium and
Phosphorous) and lipids ( yellow marrow)
4. Blood Cell Formation- hematopoiesis- occurs
within the marrow of the bone.
5. Support- for the entire body; Individual bones
provide a framework for attachment of soft
tissues and organs.
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
Classification of
Bones
• Long Bones- Relatively long and slender. (Ex:
Humerus, tibia, femur, ulna, metacarpals)
• Short Bones- Short and cube-shaped: (Ex: carpal
bones, tarsal bones)
• Flat Bones-thin, flattened, usually curved. (Ex.
Cranial bones, ribs, sternum, and bones of the hip
and shoulder girdles)
• Irregular Bones- vary in shapes, sizes, and
surface feature. (Ex:the vertebrae, patella, and a
few in the skull)
Gross Anatomy of a Long Bone
• Diaphysis
– Shaft
– Composed of compact bone
• Epiphysis
– Ends of the bone
– Composed mostly of spongy
bone
• Epiphyseal plate
(growth plate)
– a thin layer of cartilage
between the epiphysis
– a secondary bone-forming
center
Gross Anatomy of a Long Bone
• Articular cartilage
– Covers the ends of bones where
they articulate(join) with other
bones
• Periosteum
– Covers bone
– Tendons and ligaments
attachment
• Endosteum
– is a thin layer of connective
tissue that lines the surface of
the bony tissue that forms the
medullary cavity of long bones
• Medullary cavity
– The marrow cavity in the shaft
of a long bone
Gross Anatomy of a Long Bone
• Spongy bone
– Inside layer of bone
that contains red
marrow
• Compact bone
– Strong, dense layer of
bone
– Composed of cylinders
of mineral crystals
(calcium &
phosphorus) and
protein fibers
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
• Bone remodeling is a process by both osteoblasts
and osteoclasts
Bone
Tissue
Microscopic Anatomy of Bone
• Osteon (Haversian System)
– A unit of bone
• 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
Microscopic Anatomy of Bone
Microscopic Anatomy of Bone
• Canaliculi
– Tiny canals that
radiate from the
central canal to
lacunae
– Form a transport
system
Microscopic Anatomy of Bone
• Lacunae
– Cavities containing bone cells (osteocytes)
– Arranged in concentric rings
• Lamellae
– Rings around the central canal
– Sites of lacunae
Bone Development and Growth
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Bone Development and Growth
• Ossification
– The process of producing bone from cartilage.
Bone Development and Growth
• Intramembranous
bones originate
between sheetlike
layers of connective
tissue.
• Osteoblasts boneforming cells.
• Endochondral bones-Long Bones they
develop from masses of cartilage shaped like
future bony structures.
• Epiphyseal plate is the
portion of bone where
growth happens. Bones
continue to grow until the
plate closes.
• If an Epiphyseal plate is
damaged before it ossifies,
elongation of the long bone
may cease prematurely, or
growth maybe uneven.
• Babies are born with
over 300 bones; many
are composed almost
entirely of cartilage.
• The fontanels of a
baby’s skull will fuse
around age 2, but
growth of the skull
continues until
adulthood.
• Sutures develop and grow throughout
childhood at the centers of ossification
(growth plates)
• Between the ages 18 – 21, all of the
cartilage of the epiphyseal plate is replaced
by bone.
• This is called ossification and the bone
lengthening process ends.
Bone Homeostasis
• Parathyroids regulate the homeostasis of
blood calcium
• When blood calcium is low Osteoclasts tap
into reserves and Bone is “demineralized”
Calcium ions is released into blood
• Too much calcium in the blood? This
hormone causes the deposition of Calcium
into the bone matrix by osteoblasts
Low Blood Calcium
 Parathyroid gland releases parathyroid
hormone
 Stimulates osteoclasts to resorb Ca++
 Blood calcium rises
Feedback Inhibition
High Blood Calcium
 Inhibits parathyroid gland
Factors Affecting Bone
Development, Growth, and
Repair
• Deficiency of Vitamin A – retards bone development
• Deficiency of Vitamin C – results in fragile bones
• Deficiency of Vitamin D – rickets, osteomalacia
• Insufficient Growth Hormone – dwarfism
• Excessive Growth Hormone – gigantism, acromegaly
• Insufficient Thyroid Hormone – delays bone growth
• Sex Hormones – promote bone formation; stimulate ossification
of epiphyseal plates
•Insufficient Sex hormone – Osteoporosis
28
• Physical Stress – stimulates bone growth
The Skeletal System
• Divided into two
divisions
– Axial skeleton
– Appendicular skeleton
Skeletal Organization
• Axial Skeleton
• 80 bones
• head, neck , trunk
• lie along longitudinal
axis
• Appendicular Skeleton
• 126 bones
• upper & lower limbs
• pectoral & pelvic
girdle
30
The Skull
• 8 Cranial bones
– protect brain & house the ear ossicles
– muscle attachment for jaw, neck & facial muscles
• 14 Facial bones
– protect delicate sense organs -- smell, taste, vision
– support entrances to digestive and respiratory systems
31
Basic Cranial Bones
• Frontal, parietal, occipital,
and temporal.
– These make up the basic
brain case.
• Nasal, zygomatic, maxilla,
and mandible.
– The make up the front of
your face, and your jaw.
– The ears consist of 6 auditory ossicles
– Floating in the throat is the Hyoid bone.
Thoracic (Rib) cage
• Thoracic is composed of:
– 12 pairs of ribs
• True ribs—rib pairs 1
through 7
• False ribs—rib pairs 8
through 10
• Floating ribs—rib
pairs 11 and 12
– Sternum or breastbone
The vertebral column
• The vertebral column
consists of
• Cervical vertebrae (7)
– Your neck.
• Thoracic vertebrae (12)
– Attaches to your ribs.
• Lumbar vertebrae (5)
– Your lower back.
• Sacrum and coccyx
– Part of your hip and tail bone.
Appendicular skeleton
• Appendicular skeleton
consists of the
– Shoulder girdle
(pectoral girdle)
– Arms (upper limbs)
– Hip girdle (pelvic
girdle)
– Legs (lower limbs)
Pectoral Girdle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Also known as the
shoulder girdle
• Supports upper limbs
•Clavicle (2)
• Scapulae (2)
Acromial end
Sternal end
Acromion
process
Clavicle
Head of
humerus
Coracoid
process
Sternum
Scapula Rib
Costal
cartilage
Humerus
Ulna
Radius
(a)
38
Upper Limbs
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
•Consist of:
•Humerus (2)
• Radius (2)
• Ulna (2)
•Carpals
• Metacarpals
• Phalanges
Humerus
Humerus
Olecranon
process
Olecranon
fossa
Head of radius
Neck of radius
Ulna
(c)
(54)
Radius
Ulna
Ulna
Carpals
Metacarpals
Phalanges
(a) Hand (palm anterior)
(b) Hand (palm posterior)
(d)
d: © Martin Rotker
39
Pelvic Girdle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Coxal Bones (2)
• Supports trunk of body
• Protects viscera
• Forms pelvic cavity
Sacral canal
Ilium
Sacrum
Sacral hiatus
Coccyx
Ischium
(b)
Pubis
Obturator foramen
Sacroiliac joint
Ilium
Sacral promontory
Sacrum
Acetabulum
Pubis
Symphysis
pubis
Pubic tubercle
Ischium
40
Pubic arch
(a)
c: © Martin Rotker
(c)
Differences Between
Male Female Pelves
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Female pelvis
Flared ilium
• Iliac bones more flared
Sacral promontory
• Broader hips
• Pubic arch angle greater
•Lighter bones
Pelvic brim
Symphysis pubis
(a) Female pelvis
Pubic arch
Sacral promontory
Sacral curvature
41
(b) Male pelvis
Pubic arch
Lower Limb
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Femur (2)
• Patella (2)
• Tibia (2)
• Fibula (2)
• Tarsals
• Metatarsals
• Phalanges
Femur
Patella
Femur
Fibula
Tibia
(c) Lateral view
Patella
(52)
Fibula
Femur
Tibia
Lateral
condyle
Medial
condyle
Fibula
Tibia
Tarsals
Metatarsals
(d) Posterior view
42
Phalanges
(b)
Joint (Articulations)
A. Every bone except hyoid (which anchors the
tongue) connects to at least one other bone
B. Joint types classified by degree of movement
1. Synarthrosis (no movement)—fibrous connective
tissue grows between articulating bones (e.g., sutures
of skull)
2. Amphiarthrosis (slight movement)—cartilage
connects articulating bones (e.g., symphysis pubis)
43
44
Joint (Articulations)
B. Joint types
3. Diarthrosis (free movement)—most joints belong
this class
a.
b.
c.
d.
to
Structures of freely movable joints—joint capsule and
ligaments hold adjoining bones together but permit
movement at joint
Articular cartilage—covers joint ends of bones and absorbs
jolts
Synovial membrane—lines joint capsule and secretes
lubricating fluid
Joint cavity—space between joint ends of bones
45
Joint (Articulations)
C. Freely movable joints
–
–
–
–
–
–
Ball-and-socket
Hinge
Pivot
Saddle
Gliding
Condyloid
46
47
48
Skeletal Disorders
A. Bone fractures
1. Open (compound) fractures pierce the skin
and closed (simple) fractures do not
2. Fracture types include complete and
incomplete, linear, transverse and oblique
49
50
How does a broken bone heal?
1. Blood flow increases to the area
of the break. This allows nutrients
and oxygen to help the healing
process.
2. As bone becomes
deposited, it grows
stronger, and eventually
remodels itself.
1. Conversion of blood clot (hematoma) to a soft
tissue procallus.
 Takes 48 hours
 Loose network of fibers is laid down
 Inflammatory reaction = swelling =
edema
 Increased blood flow and infiltration
by white blood cells
 Macrophages phagocytize debris
 Fibroblasts begin repair process
by laying down connective tissue
Skeletal Disorders
B. Joint disorders
1. Noninflammatory joint disorders—do not usually
involve inflammation of the synovial membrane;
symptoms tend to be local and not systemic
a. Osteoarthritis, or degenerative joint disease (DJD)
1) Most common noninflammatory disorder of movable joints—
often called “wear and tear” arthritis
2) Symptoms: joint pain, morning stiffness, Bouchard nodes (at
proximal interphalangeal joints), Heberden nodes (at distal
interphalangeal joints) of the fingers
3) Most common cause for partial and total hip and knee
replacements
53
54
Skeletal Disorders
• Joint disorders
1. Noninflammatory joint disorders
b. Traumatic injury
1) Dislocation or subluxation—articular surfaces of bones
in joint are no longer in proper contact
2) Sprain—acute injury to ligaments around joints (e.g.,
whiplash type injuries)
3) Strain—acute injury to any part of the
“musculotendinous unit” (muscle, tendon, junction
between the two, and attachments to bone)
55
Skeletal Disorders
• Joint disorders
2. Inflammatory joint disorders
• Arthritis: general name for several inflammatory
joint diseases that may be caused by infection,
injury, genetic factors, and autoimmunity
• Inflammation of the synovial membrane occurs,
often with systemic signs and symptoms
56
Skeletal Disorders
– Inflammatory joint disorders: Arthritis
a. Rheumatoid arthritis
Systemic autoimmune disease—chronic inflammation of synovial
membrane with involvement of other tissues such as blood
vessels, eyes, heart, and lungs
b. Gouty arthritis
synovial inflammation caused by gout, a condition in which
sodium urate crystals (URIC ACID) form in joints and other
tissues
c. Infectious arthritis
arthritis resulting from infection by a pathogen, as in Lyme
arthritis and ehrlichiosis, caused by two different bacteria that are
transmitted to humans by tick bites
57
58
Skeletal Disorders
C. Tumors of bone and cartilage
1. Osteosarcoma
a.
b.
Most common and serious malignant bone neoplasm
Frequent sites include distal femur and proximal tibia and
humerus
2. Chondrosarcoma
a.
b.
c.
Cancer of skeletal hyaline cartilage
Second most common cancer of skeletal tissues
Frequent sites include medullary cavity of humerus, femur,
ribs, and pelvic bones
59
60
Skeletal Disorders
D. Metabolic bone diseases
1. Osteoporosis
a. Characterized by loss of calcified bone matrix and
reduction in number of trabeculae in spongy bone
b. Bones fracture easily, especially in wrists, hips,
and vertebrae
c. Treatment includes drug therapy, exercise, and
dietary supplements of calcium and vitamin D
61
62
Skeletal Disorders
• Metabolic bone diseases
2. Rickets and osteomalacia—both diseases
characterized by loss of bone minerals related
to vitamins
a. Rickets
– Loss of bone minerals occurs in infants and young
children before skeletal maturity
– Lack of bone rigidity causes gross skeletal changes
(bowing of legs)
– Treated with vitamin D
63
64
Skeletal Disorders
• Metabolic bone diseases
2. Rickets and osteomalacia
b. Osteomalacia
– Mineral content is lost from bones that have already
matured
– Increases susceptibility to fractures
– Treated with vitamin D
65
Skeletal Disorders
• Metabolic bone diseases
3. Paget disease (osteitis deformans)
• Faulty remodeling results in deformed bones that
fracture easily
• Cause may be genetic or triggered by viral
infections
66
67
Skeletal Disorders
• Metabolic bone diseases
4. Osteogenesis imperfecta (also called brittle
bone disease)
• Bones are brittle because of lack of organic matrix
• Treatment may include splinting to reduce fracture
and drugs that decrease cell activity
68
69
Skeletal Disorders
E. Bone infection
1. Osteomyelitis
• General term for bacterial (usually staphylococcal)
infection of bone
• Treatment may involve surgery, drainage of pus,
and IV antibiotic treatment—often over prolonged
periods
70
71
About Spinal Curvature
• At birth your spinal Column is shaped like a
C
• When baby is about to crawl the cervical
region curves towards posterior.
• As toddler begins to walk, another curve
sets in the lumber area in the same
direction…resulting in its characteristic S
shape.
Spinal Maladies
• Kyphosis or Hunchback- When too much
thoracic curvature (usually a result of
osteoporosis)
• Lordosis- Exaggerated Lumbar curvature ( may
result from too much weight in pregnancy or
obesity)
• Scolliosis- A developmental abnormality in
thoracic region (abnormal lateral curvature):
can be corrected w/ a back brace.
• Herniated Disk
What do you think happens if
you have a “blown disc”?
• Your cartilage is located
between your vertebrae.
• When the tissue surrounding
your disc ruptures, it allows
your cartilage to move.
– “Herniated disc”
• This movement can pinch
surrounding nerves, causing
back pain.
Rickets:
 Vitamin D deficiency in growing children
 Unable to absorb calcium and phosphate from
gut
 Inorganic bone matrix (mineral salts) lacks
calcium Bones deform
Gouty Arthritis (GOUT)
– Inflammation of joints is caused by a
deposition of urate (URIC ACID) crystals
from the blood
– Can usually be controlled with diet
– Hereditary as it runs in families.
– This is very painful!!
Cartilaginous Joints
• Bones connected by cartilage
• Examples
– Pubic
symphysis
– Intervertebral
joints
Figure 5.27d–e
Synovial Joints
• Articulating
bones are
separated by a
joint cavity
• Synovial fluid is
found in the
joint cavity
Figure 5.24f–h
The Synovial Joint
Figure 5.28
Joseph Merrick
• Lived 1862 – 1890 in
England
• Known as the “Elephant
Man” due to his deformities
• Thought to be either Proteus
Syndrome or
Neurofibromatosis
• Caused great enlargement of
bone and surrounding tissue
• Died due to a dislocation of
the neck (strain from head
weight)