5 The Skeletal System.

5 The Skeletal System

The Skeletal System Parts of the skeletal system Bones (skeleton)
Joints Cartilages Ligaments (connect two or more bones) Two subdivisions of the skeleton Axial skeleton Appendicular skeleton

Functions of Bones Support the body Protect soft organs
Skull and vertebrae for brain and spinal cord Rib cage for thoracic cavity organs Allow movement due to attached skeletal muscles Store minerals and fats Calcium and phosphorus Fat in the internal marrow cavity Blood cell formation (hematopoiesis)

Spongy bone Compact bone Figure 5.1

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 on the Basis of Shape
Bones are classified as: Long Short Flat Irregular

Figure 5.2

Classification of Bones
Long bones Typically longer than they are wide Shaft with heads situated at both ends Contain mostly compact bone All of the bones of the limbs (except wrist, ankle, and kneecap bones) Example: Femur Humerus

Figure 5.2a

Short bones Generally cube-shaped Contain mostly spongy bone Includes bones of the wrist and ankle Sesamoid bones are a type of short bone which form within tendons (patella) Example: Carpals Tarsals

Figure 5.2d

Flat bones Thin, flattened, and usually curved Two thin layers of compact bone surround a layer of spongy bone Example: Skull Ribs Sternum

Spongy bone Compact bone Figure 5.1

Figure 5.2c

Irregular bones Irregular shape Do not fit into other bone classification categories Example: Vertebrae Hip bones

Figure 5.2b

Anatomy of a Long Bone Diaphysis Shaft Composed of compact bone
Epiphysis Ends of the bone Composed mostly of spongy bone

Articular cartilage Proximal epiphysis Spongy bone Epiphyseal line
Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis (a) Figure 5.3a

Anatomy of a Long Bone Periosteum Outside covering of the diaphysis
Fibrous connective tissue membrane Perforating (Sharpey’s) fibers Secure periosteum to underlying bone Arteries Supply bone cells with nutrients

Endosteum Yellow bone marrow Compact bone Periosteum Perforating
(Sharpey’s) fibers Nutrient arteries (c) Figure 5.3c

Anatomy of a Long Bone Articular cartilage
Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces

Articular cartilage Compact bone Spongy bone (b) Figure 5.3b

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

Anatomy of a Long Bone Marrow (medullary) cavity
Cavity inside of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow for blood cell formation in infants In adults, red marrow is situated in cavities of spongy bone and epiphyses of long bones

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 Terms often begin with “T” Depressions or cavities—indentations Terms often begin with “F”

Osteon (Haversian system) Lamellae Blood vessel continues into medullary cavity containing marrow Spongy bone Perforating fibers Compact bone Periosteal blood vessel Central (Haversian) canal Periosteum Perforating (Volkmann’s) canal (a) Blood vessel Figure 5.4a

Microscopic Anatomy of Compact Bone
Osteon (Haversian system) A unit of bone containing central canal and matrix rings Central (Haversian) canal Opening in the center of an osteon Carries blood vessels and nerves Perforating (Volkmann’s) canal Canal perpendicular to the central canal

Microscopic Anatomy of Bone
Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings called lamellae Lamellae Rings around the central canal Sites of lacunae

Canaliculus Lacuna (b)
Lamella Osteocyte Canaliculus Lacuna (b) Central (Haversian) canal Figure 5.4b

Osteon Lacuna (c) Central canal Interstitial lamellae Figure 5.4c

Microscopic Anatomy of Bone
Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system connecting all bone cells to a nutrient supply

Canaliculus Lacuna (b)
Lamella Osteocyte Canaliculus Lacuna (b) Central (Haversian) canal Figure 5.4b

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)

Articular cartilage Hyaline cartilage Spongy bone New center of
bone growth New bone forming Epiphyseal plate cartilage Growth in bone width Medullary cavity Bone starting to replace cartilage Invading blood vessels Growth in bone length New bone forming Bone collar Hyaline cartilage model Epiphyseal plate cartilage In an embryo In a fetus In a child Figure 5.5

Bone starting to replace cartilage Bone collar Hyaline cartilage model
In an embryo Figure 5.5, step 1

Hyaline cartilage New center of bone growth Medullary cavity Invading
blood vessels Growth in bone length In a fetus Figure 5.5, step 2

Articular cartilage Spongy bone New bone forming Epiphyseal plate
Growth in bone width Invading blood vessels New bone forming Epiphyseal plate cartilage In a child Figure 5.5, step 3

is replaced by bone here. 4 Bone is resorbed here. 3
Bone growth Bone remodeling Bone grows in length because: Growing shaft is remodeled as: Articular cartilage Cartilage grows here. 1 Epiphyseal plate Cartilage is replaced by bone here. 2 1 Bone is resorbed here. Cartilage grows here. 3 2 Bone is added by appositional growth here. Cartilage is replaced by bone here. 4 Bone is resorbed here. 3 Figure 5.6

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 into the bloodstream Bone remodeling is performed by both osteoblasts and osteoclasts

Wolff’s Law States that healthy bone will adapt to the loads under which it is placed. Stress is detected by osteocytes. The osteocytes will signal for increased osteoblast activity in these areas.

Wolff’s Law Examples Tennis players racquet arms are consistently larger and more dense than their non-racquet arms

Wolff’s Law Examples “Surfer’s Knots” occur from chronic stress usually to top of the foot or knees.

Surfer’s Knots Fun Facts
In the late 60’s people would surf excessively to build up the knots on their feet. This would prevent them from being able to fit into a standard issue military boot, therefore disqualifying them from the draft for the Vietnam War.

Wolff’s Law Examples Bones also respond to the lack of stress.
Astronauts typically lose 1-2% of overall bone mass per month spent in space. Calcium, vitamin D supplements, growth hormones and exercise regiments are all implemented by astronauts to prevent bone loss. No methods have been found to definitively prevent bone loss during space travel

Astronaut Bone Loss Bone density loss is a real concern NASA is studying as long-term space travel missions are being planned. Maybe you can help resolve this issue..!!...!!

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

Common Types of Fractures
Comminuted—bone breaks into many fragments Compression—bone is crushed Depressed—broken bone portion is pressed inward Impacted—broken bone ends are forced into each other Spiral—ragged break occurs when excessive twisting forces are applied to a bone Greenstick—bone breaks incompletely

Table 5.2 Common Types of Fractures

Repair of Bone Fractures
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

Figure 5.7 Hematoma External callus Bony callus of spongy bone New
blood vessels Internal callus (fibrous tissue and cartilage) Healed fracture Spongy bone trabecula Hematoma forms. 1 Fibrocartilage callus forms. 2 Bony callus forms. 3 Bone remodeling occurs. 4 Figure 5.7

Hematoma Hematoma forms. 1 Figure 5.7, step 1

Figure 5.7, step 2 Hematoma External callus New blood vessels Internal
(fibrous tissue and cartilage) Spongy bone trabecula Hematoma forms. 1 Fibrocartilage callus forms. 2 Figure 5.7, step 2

Figure 5.7, step 3 Hematoma External callus Bony callus of spongy bone
New blood vessels Internal callus (fibrous tissue and cartilage) Spongy bone trabecula Hematoma forms. 1 Fibrocartilage callus forms. 2 Bony callus forms. 3 Figure 5.7, step 3

Figure 5.7, step 4 Hematoma External callus Bony callus of spongy bone
New blood vessels Internal callus (fibrous tissue and cartilage) Healed fracture Spongy bone trabecula Hematoma forms. 1 Fibrocartilage callus forms. 2 Bony callus forms. 3 Bone remodeling occurs. 4 Figure 5.7, step 4

The Axial Skeleton Forms the longitudinal axis of the body
Divided into three parts Skull Vertebral column Bony thorax

Figure 5.8a Cranium Skull Facial bones Clavicle Thoracic cage Scapula
(ribs and sternum) Scapula Sternum Rib Humerus Vertebra Vertebral column Radius Ulna Sacrum Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior view Figure 5.8a

Figure 5.8b Cranium Bones of pectoral girdle Clavicle Scapula Upper
limb Rib Humerus Vertebra Radius Bones of pelvic girdle Ulna Carpals Phalanges Metacarpals Femur Lower limb Tibia Fibula (b) Posterior view Figure 5.8b

The Skull Two sets of bones Cranium Facial bones
Bones are joined by sutures Only the mandible is attached by a freely movable joint

Coronal suture Frontal bone Parietal bone Sphenoid bone Temporal bone Ethmoid bone Lambdoid suture Lacrimal bone Squamous suture Nasal bone Occipital bone Zygomatic bone Zygomatic process Maxilla External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible (body) Mental foramen Mandibular ramus Figure 5.9

Frontal bone Cribriform plate Ethmoid bone Crista galli Sphenoid bone Optic canal Sella turcica Foramen ovale Temporal bone Jugular foramen Internal acoustic meatus Parietal bone Occipital bone Foramen magnum Figure 5.10

Maxilla (palatine process) Hard palate Palatine bone Maxilla
Zygomatic bone Sphenoid bone (greater wing) Temporal bone (zygomatic process) Foramen ovale Vomer Mandibular fossa Carotid canal Styloid process Mastoid process Jugular foramen Occipital condyle Temporal bone Parietal bone Foramen magnum Occipital bone Figure 5.11

Coronal suture Frontal bone Parietal bone Nasal bone Superior orbital fissure Sphenoid bone Optic canal Ethmoid bone Temporal bone Lacrimal bone Zygomatic bone Middle nasal concha of ethmoid bone Maxilla Inferior nasal concha Vomer Mandible Alveolar processes Figure 5.12

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

Frontal sinus Ethmoid sinus Sphenoidal sinus Maxillary sinus
(a) Anterior view Figure 5.13a

Frontal sinus Ethmoid sinus Sphenoidal sinus Maxillary sinus
(b) Medial view Figure 5.13b

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

Greater horn Lesser horn Body Figure 5.14

The Fetal Skull The fetal skull is large compared to the infant’s total body length Fetal skull is 1/4 body length compared to adult skull which is 1/8 body length Fontanels—fibrous membranes connecting the cranial bones Allow skull compression during birth Allow the brain to grow during later pregnancy and infancy Convert to bone within 24 months after birth

Anterior fontanel Frontal bone Parietal bone Posterior fontanel
Occipital bone (a) Figure 5.15a

Anterior fontanel Sphenoidal fontanel Parietal bone Frontal bone
Posterior fontanel Occipital bone Mastoid fontanel Temporal bone (b) Figure 5.15b

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 are in the neck Twelve thoracic vertebrae are in the chest region Five lumbar vertebrae are associated with the lower back

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

The Vertebral Column Nine vertebrae fuse to form two composite bones
Sacrum Coccyx

Anterior Posterior 1st cervical vertebra (atlas) Cervical curvature (concave) 7 vertebrae, C1 – C7 2nd cervical vertebra (axis) 1st thoracic vertebra Transverse process Spinous process Thoracic curvature (convex) 12 vertebrae, T1 – T12 Intervertebral disc Intervertebral foramen 1st lumbar vertebra Lumbar curvature (concave) 5 vertebrae, L1 – L5 Sacral curvature (convex) 5 fused vertebrae Coccyx 4 fused vertebrae Figure 5.16

The Vertebral Column Primary curvatures are the spinal curvatures of the thoracic and sacral regions Present from birth Form a C-shaped curvature as in newborns Secondary curvatures are the spinal curvatures of the cervical and lumbar regions Develop after birth Form an S-shaped curvature as in adults

Figure 5.17

Figure 5.18

A Typical Vertebrae Body Vertebral arch Pedicle Lamina
Vertebral foramen Transverse processes Spinous process Superior and inferior articular processes

Posterior Vertebral Lamina arch Transverse Spinous process process
Superior articular process and facet Pedicle Vertebral foramen Body Anterior Figure 5.19

(a) ATLAS AND AXIS Transverse process Posterior arch Anterior arch Superior view of atlas (C1) Spinous process Transverse process Facet on superior articular process Dens Body Superior view of axis (C2) Figure 5.20a

(b) TYPICAL CERVICAL VERTEBRAE
Facet on superior articular process Spinous process Vertebral foramen Transverse process Superior view Superior articular process Body Spinous process Transverse process Facet on inferior articular process Right lateral view Figure 5.20b

(c) THORACIC VERTEBRAE
Spinous process Transverse process Vertebral foramen Facet for rib Facet on superior articular process Body Superior view Facet on superior articular process Body Facet on transverse process Costal facet for rib Spinous process Right lateral view Figure 5.20c

(d) LUMBAR VERTEBRAE Spinous process Vertebral foramen Transverse process Facet on superior articular process Body Superior view Superior articular process Body Spinous process Facet on inferior articular process Right lateral view Figure 5.20d

Superior articular process Auricular surface Sacral canal Ala Body Median sacral crest Sacrum Posterior sacral foramina Sacral hiatus Coccyx Figure 5.21

The Bony Thorax Forms a cage to protect major organs
Consists of three parts Sternum Ribs True ribs (pairs 1–7) False ribs (pairs 8–12) Floating ribs (pairs 11–12) Thoracic vertebrae

T1 vertebra Jugular notch Clavicular notch Manubrium Sternal angle
Body Sternum Xiphisternal joint True ribs (1 –7) Xiphoid process False ribs (8 –12) Intercostal spaces L1 Vertebra Costal cartilage Floating ribs (11, 12) (a) Figure 5.22a

T2 Jugular notch T3 T4 Sternal angle Heart Xiphisternal T9 joint (b)
Figure 5.22b

The Appendicular Skeleton
Composed of 126 bones Limbs (appendages) Pectoral girdle Pelvic girdle

Figure 5.8a Cranium Skull Facial bones Clavicle Thoracic cage Scapula
(ribs and sternum) Scapula Sternum Rib Humerus Vertebra Vertebral column Radius Ulna Sacrum Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior view Figure 5.8a

Figure 5.8b Cranium Bones of pectoral girdle Clavicle Scapula Upper
limb Rib Humerus Vertebra Radius Bones of pelvic girdle Ulna Carpals Phalanges Metacarpals Femur Lower limb Tibia Fibula (b) Posterior view Figure 5.8b

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 Terms often begin with “T” Depressions or cavities—indentations Terms often begin with “F”

The Pectoral (Shoulder) Girdle
Composed of two bones Clavicle—collarbone Articulates with the sternum medially and with the scapula laterally Scapula—shoulder blade Articulates with the clavicle at the acromioclavicular joint Articulates with the arm bone at the glenoid cavity These bones allow the upper limb to have exceptionally free movement

Acromio clavicular joint Clavicle Scapula (a) Articulated right shoulder (pectoral) girdle showing the relationship to bones of the thorax and sternum Figure 5.23a

Acromial (lateral) end Anterior
Posterior Sternal (medial) end Acromial (lateral) end Anterior Superior view Acromial end Sternal end Anterior Posterior Inferior view (b) Right clavicle, superior and inferior views Figure 5.23b

Glenoid cavity at lateral angle
Coracoid process Suprascapular notch Superior angle Acromion Glenoid cavity at lateral angle Spine Medial border Lateral border (c) Right scapula, posterior aspect Figure 5.23c

(d) Right scapula, anterior aspect
Acromion Suprascapular notch Superior border Coracoid process Superior angle Glenoid cavity Lateral (axillary) border Medial (vertebral) border Inferior angle (d) Right scapula, anterior aspect Figure 5.23d

Bones of the Upper Limbs
Humerus Forms the arm Single bone Proximal end articulates with the glenoid cavity of the scapula Distal end articulates with the bones of the forearm

Head of humerus Greater tubercle Lesser tubercle Anatomical neck Intertubercular sulcus Deltoid tuberosity Radial fossa Medial epicondyle Coronoid fossa Capitulum Trochlea (a) Figure 5.24a

Head of humerus Anatomical neck Surgical neck Radial groove Deltoid tuberosity Medial epicondyle Olecranon fossa Lateral epicondyle Trochlea (b) Figure 5.24b

Trochlear notch Olecranon Head Coronoid process Neck Proximal radioulnar joint Radial tuberosity Radius Ulna Inter- osseous membrane Ulnar styloid process Radial styloid process Distal radioulnar joint (c) Figure 5.24c

The forearm has two bones Ulna—medial bone in anatomical position Proximal end articulates at olecranon process with Coronoid fossa of the humerus Radius—lateral bone in anatomical position Proximal end head articulates with the capitulum of the humerus

RADIUS IS

Distal Middle Phalanges (fingers) Proximal 3 2 4 Metacarpals (palm) 5
1 Hamate Trapezium Carpals (wrist) Pisiform Trapezoid Triquetrum Scaphoid Lunate Capitate Ulna Radius Figure 5.25

Hand Carpals—wrist Eight bones arranged in two rows of four bones in each hand Metacarpals—palm Five per hand Phalanges—fingers and thumb Fourteen phalanges in each hand In each finger, there are three bones In the thumb, there are only two bones

Bones of the Pelvic Girdle
Formed by two coxal (ossa coxae) bones Composed of three pairs of fused bones Ilium Ischium Pubis Pelvic girdle = 2 coxal bones, sacrum Bony pelvis 2 coxal bones (pelvis), sacrum, coccyx

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

lliac crest Sacroiliac joint llium Coxal bone (or hip bone) Sacrum Pelvic brim Pubis Coccyx Ischial spine Acetabulum Ischium Pubic symphysis Pubic arch (a) Figure 5.26a

Posterior superior iliac spine
IIium Ala IIiac crest Posterior superior iliac spine Anterior superior iliac spine Posterior inferior iliac spine Anterior inferior iliac spine Greater sciatic notch Acetabulum Ischial body Body of pubis Ischial spine Pubis Ischial tuberosity Inferior pubic ramus Ischium Obturator foramen Ischial ramus (b) Figure 5.26b

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

Pubic arch (less than 90°)
False pelvis Inlet of true pelvis Pelvic brim Pubic arch (less than 90°) False pelvis Inlet of true pelvis Pelvic brim Pubic arch (more than 90°) (c) Figure 5.26c

Bones of the Lower Limbs
Femur—thigh bone The heaviest, strongest bone in the body Proximal end articulation Head articulates with the acetabulum of the pelvis bone Distal end articulation Lateral and medial condyles articulate with the tibia in the lower leg

Neck Head Inter- trochanteric line Lesser trochanter Lateral condyle Patellar surface (a) Figure 5.27a

Inter- trochanteric crest
Greater trochanter Head Inter- trochanteric crest Lesser trochanter Gluteal tuberosity Intercondylar fossa Medial condyle Lateral condyle (b) Figure 5.27b

Intercondylar eminence
Lateral condyle Medial condyle Head Tibial tuberosity Proximal tibiofibular joint Interosseous membrane Anterior border Fibula Tibia Distal tibiofibular joint Medial malleolus Lateral malleolus (c) Figure 5.27c

The lower leg has two bones Tibia—Shinbone; larger and medially oriented Proximal end articulation Medial and lateral condyles articulate with the femur to form the knee joint Fibula—Thin and sticklike; lateral to the tibia Has no role in forming the knee joint

Intermediatecuneiform Lateral cuneiform
Phalanges: Distal Middle Proximal Tarsals: Medial cuneiform Metatarsals Tarsals: Intermediatecuneiform Lateral cuneiform Navicular Cuboid Talus Calcaneus Figure 5.28

The foot Tarsals—seven bones Two largest tarsals Calcaneus (heel bone) Talus Metatarsals—five bones form the sole of the foot Phalanges—fourteen bones form the toes

Arches of the Foot Bones of the foot are arranged to form three strong arches Two longitudinal One transverse

Medial longitudinal arch
Transverse arch Lateral longitudinal arch Figure 5.29

Joints Articulations of bones Functions of joints Hold bones together
Allow for mobility Two 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

Fibrous Joints Bones united by collagenic fibers Types Sutures
Immobile Syndesmoses Allows more movement than sutures but still immobile Example: Distal end of tibia and fibula Gomphosis

Fibrous joints Fibrous connective tissue (a) Suture Figure 5.30a

Fibrous joints Tibia Fibula Fibrous connective tissue (b) Syndesmosis Figure 5.30b

Cartilaginous Joints Bones connected by cartilage Types Synchrondrosis
Immobile Symphysis Slightly movable Example: Pubic symphysis, intervertebral joints

Cartilaginous joints First rib Hyaline cartilage Sternum (c) Synchondrosis Figure 5.30c

Cartilaginous joints Vertebrae Fibrocartilage (d) Symphysis Figure 5.30d

Cartilaginous joints Pubis Fibro- cartilage (e) Symphysis Figure 5.30e

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

Articular (hyaline) cartilage
Synovial joints Scapula Articular capsule Articular (hyaline) cartilage Humerus (f) Multiaxial joint (shoulder joint) Figure 5.30f

Synovial joints Humerus Articular (hyaline) cartilage Articular capsule Radius Ulna (g) Uniaxial joint (elbow joint) Figure 5.30g

(intercarpal joints of hand)
Synovial joints Ulna Radius Articular capsule Carpals (h) Biaxial joint (intercarpal joints of hand) Figure 5.30h

Features of Synovial Joints
Articular cartilage (hyaline cartilage) covers the ends of bones Articular capsule encloses joint surfaces and lined with synovial membrane Joint cavity is filled with synovial fluid Reinforcing ligaments

Structures Associated with the Synovial Joint
Bursae—flattened fibrous sacs Lined with synovial membranes Filled with Not actually part of the joint synovial fluid Tendon sheath Elongated bursa that wraps around a tendon

Joint cavity containing synovial fluid
Acromion of scapula Ligament Joint cavity containing synovial fluid Bursa Ligament Articular (hyaline) cartilage Tendon sheath Synovial membrane Fibrous layer of the articular capsule Tendon of biceps muscle Humerus Figure 5.31

Nonaxial Uniaxial Biaxial Multiaxial (a) Plane joint (a) Figure 5.32a

Nonaxial Uniaxial Biaxial Multiaxial (b) Humerus Ulna (b) Hinge joint
Figure 5.32b

Nonaxial Uniaxial Biaxial Multiaxial Ulna (c) Radius (c) Pivot joint
Figure 5.32c

Nonaxial Uniaxial Biaxial Multiaxial (d) Metacarpal Phalanx (d) Condylar joint Figure 5.32d

Nonaxial Uniaxial Biaxial Multiaxial Carpal Metacarpal #1 (e)
(e) Saddle joint Figure 5.32e

(f) Ball-and-socket joint
Nonaxial Uniaxial Biaxial Multiaxial (f) Head of humerus Scapula (f) Ball-and-socket joint Figure 5.32f

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 Initial symptoms: pain, stiffness, swelling of the joint

Clinical Forms of Arthritis
Osteoarthritis Most common chronic arthritis Due to normal “wear and tear of 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

Figure 5.33

Clinical Forms of Arthritis
Gouty arthritis Inflammation of joints is caused by a deposition of uric acid crystals from the blood Can usually be controlled with diet More common in men

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

Parietal bone Frontal bone of skull Occipital bone Mandible Clavicle
Scapula Radius Ulna Humerus Femur Tibia Ribs Vertebra Hip bone Figure 5.34

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 cranium in relationship to body 2 years old—skull is larger in proportion to the body compared to that of an adult 8 or 9 years old—skull is near adult size and proportion Between ages 6 and 11, the face grows out from the skull

Figure 5.35a

Figure 5.35b

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

Figure 5.18

Osteoporosis Bone-thinning disease afflicting 50 percent of women over age 65 20 percent 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

Figure 5.36

Figure 5.37

5 The Skeletal System.

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