Chapter 7Skeletal System

Bone Classification

• Long Bones• Short Bones• Flat Bones• Irregular Bones• Sesamoid Bones

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Parts of a Long Bone• epiphysis- expanded end of long bone

• distal• proximal

• diaphysis-shaft

• compact bone-outer surface • spongy bone- cancellous bone, which contain bony plates called trabeculae. Found at the epiphysis of long bone.

• periosteum-tough, vascular membrane covering the outer surface.

• medullary cavity -hollow space found in the diaphysis and spaces of spongy bone• endosteum - thin membrane lining the cavity-contains bone forming cell.

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• marrow-

red yellow

Major parts of long bone

Compact and Spongy Bone

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Spongy bone• Location:• Flat bones, irregular bones, and end of long bones• Osteocytes- lie within the bony plates• No central canal• A layer of spongy sandwiched between plates of

compact bone• In an adult, red marrow, is found in the spongy bone

of all flat bones.• In an infant, red marrow occupies the cavities of

long bone. Yellow marrow stores fat and fills the cavity in an adult.

• Location:• Flat bones, irregular bones, and end of long bones• Osteocytes- lie within the bony plates• No central canal• A layer of spongy sandwiched between plates of

compact bone• In an adult, red marrow, is found in the spongy bone

of all flat bones.• In an infant, red marrow occupies the cavities of

long bone. Yellow marrow stores fat and fills the cavity in an adult.

Compact bone• In compact bone, the osteocyte's lie concentrically

around a central canal. Each unit forms an osteon cemented together to form compact bone.

• Central canals - contains blood vessels and nerve fibers, which provide nutrients for bone cells.

• Transverse canals interconnect with the central canals, allowing communication between each osteon and the surface of bone.

• Collagen gives bone strength and inorganic salts make it hard and resistant.

• In compact bone, the osteocyte's lie concentrically around a central canal. Each unit forms an osteon cemented together to form compact bone.

• Central canals - contains blood vessels and nerve fibers, which provide nutrients for bone cells.

• Transverse canals interconnect with the central canals, allowing communication between each osteon and the surface of bone.

• Collagen gives bone strength and inorganic salts make it hard and resistant.

Microscopic Structureof Compact Bone

• osteon• central canal• perforating canal• osteocyte• lacuna• bone matrix• canaliculus

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Bone Development

Intramembranous Ossification• bones originate within sheetlike layers of connective tissues• broad, flat bones• skull bones (except mandible)• intramembranous bones

Endochondral Ossification• bones begin as hyaline cartilage• most bones of the skeleton• endochondral bones

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Endochondral Ossification

• hyaline cartilage model• primary ossification center• secondary ossification centers

• epiphyseal plate• osteoblasts vs. osteoclasts

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Growth at the Epiphyseal Plate

First layer of cells• closest to the end of epiphysis• resting cells• anchors epiphyseal plate to epiphysis

Second layer of cells• many rows of young cells• undergoing mitosis

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Growth at the Epiphyseal Plate

Third layer of cells• older cells• left behind when new cells appear• cells enlarging and becoming calcified

Fourth layer of cells• thin• dead cells• calcified intercellular substance

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Homeostasis of Bone Tissue

•Bone Resorption – action of osteoclasts and parathyroid hormone•Bone Deposition – action of osteoblasts and calcitonin

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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• Physical Stress – stimulates bone growth

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Levers and Movement

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Skeletal Organization

Axial Skeleton• head • neck • trunk

Appendicular Skeleton• upper limbs• lower limbs• pectoral girdle• pelvic girdle

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Skeletal Organization

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Skull

Frontal (1)• forehead• roof of nasal cavity• roofs of orbits• frontal sinuses• supraorbital foramen• coronal suture

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Skull

Parietal (2)• side walls of cranium• roof of cranium• sagittal suture

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Skull

Temporal (2)• wall of cranium• floor of cranium• floors and sides of orbits• squamosal suture• external acoustic meatus• mandibular fossa• mastoid process• styloid process• zygomatic process

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Skull

Occipital (1)• back of skull• base of cranium• foramen magnum• occipital condyles• lambdoidal suture

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Skull

Sphenoid (1)• base of cranium• sides of skull• floors and sides of orbits• sella turcica• sphenoidal sinuses

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Skull

Ethmoid (1)• roof and walls of nasal cavity• floor of cranium• wall of orbits• cribiform plates• perpendicular plate• superior and middle nasal conchae• ethmoidal sinuses• crista gallis

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Facial Skeleton

Maxillary (2)• upper jaw• anterior roof of mouth• floors of orbits• sides of nasal cavity• floors of nasal cavity• alveolar processes• maxillary sinuses• palatine process

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Facial Skeleton

Palatine (2)• posterior roof of mouth• floor of nasal cavity• lateral walls of nasal cavity

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Facial Skeleton

Zygomatic (2) • prominences of cheeks• lateral walls of orbits• floors of orbits• temporal process

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Facial Skeleton

Lacrimal (2)• medial walls of orbits• groove from orbit to nasal cavity

Nasal (2)• bridge of nose

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Facial Skeleton

Vomer (1)• inferior portion of nasal septum

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Facial Skeleton

Inferior Nasal Conchae (2)• extend from lateral walls of nasal cavity

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Facial Skeleton

Mandible (1)• lower jaw• body• ramus• mandibular condyle• coronoid process• alveolar process• mandibular foramen• mental foramen

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Vertebral Column• cervical vertebrae C1—c7

• thoracic vertebrae T1-T12

• lumbar vertebrae L1-L5

• sacrum S1-S5

• coccyx 5-fused

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Vertebral Column

• cervical curvature• thoracic curvature• lumbar curvature• pelvic curvature• rib facets• vertebra prominens• intervertebral discs• intervertebral foramina

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Cervical Vertebrae

• Atlas – 1st; supports head• Axis – 2nd; dens pivots to turn head• transverse foramina• bifid spinous processes• vertebral prominens – useful landmark

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Thoracic Vertebrae

• long spinous processes• rib facets

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Lumbar Vertebrae

• large bodies• thick, short spinous processes

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Sacrum

• five fused vertebrae• median sacral crest• dorsal sacral foramina• posterior wall of pelvic cavity• sacral promontory

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Coccyx

• tailbone• four fused vertebrae

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Thoracic Cage

• Ribs• Sternum• Thoracic vertebrae• Costal cartilages• Supports shoulder girdle• Protects viscera• Role in breathing

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Ribs

• True ribs (7)• False ribs (5)

• floating (2)

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Rib Structure

• Shaft• Head – posterior end; articulates with vertebrae• Tubercle – articulates with vertebrae• Costal cartilage – hyaline cartilage

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Sternum

• Manubrium• Body• Xiphoid process

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Pectoral Girdle

• shoulder girdle • clavicles• scapulae• supports upper limbs

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Clavicles

• articulate with manubrium• articulate with scapulae (acromion process)

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Scapulae

• spine• supraspinous fossa• infraspinous fossa

• acromion process• coracoid process• glenoid cavity

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Upper Limb

• Humerus• Radius• Ulna• Carpals• Metacarpals• Phalanges

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Humerus

• head• greater tubercle• lesser tubercle• anatomical neck• surgical neck• deltoid tuberosity• capitulum• trochlea• coronoid fossa• olecranon fossa

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Radius

• lateral forearm bone• head• radial tuberosity• styloid process

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Ulna

• medial forearm bone• trochlear notch• olecranon process• coronoid process• styloid process

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Wrist and Hand

• Carpals (16)• trapezium• trapezoid• capitate• scaphoid• pisiform• triquetrum• hamate• lunate

• Metacarpals (10)

• Phalanges (28)• proximal phalanx• middle phalanx• distal phalanx

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Pelvic Girdle

• Coxae (2)• supports trunk of body• protects viscera

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Coxae

• hip bones• ilium

• iliac crest• iliac spines• greater sciatic notch

• ischium• ischial spines• lesser sciatic notch• ischial tuberosity

• pubis• obturator foramen• acetabulum

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Greater and Lesser Pelvis

Greater Pelvis• lumbar vertebrae posteriorly• iliac bones laterally• abdominal wall anteriorly

Lesser Pelvis• sacrum and coccyx posteriorly• lower ilium, ischium, and pubis bones laterally and anteriorly

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Male and Female Pelvis

Female• iliac bones more flared• broader hips• pubic arch angle greater• more distance between ischial spine and ischial tuberosity• sacral curvature shorter and flatter• lighter bones

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Lower Limb

• Femur• Patella• Tibia• Fibula• Tarsals• Metatarsals• Phalanges

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Femur

• longest bone of body• head• fovea capitis• neck• greater trochanter• lesser trochanter• linea aspera• condyles• epicondyles

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Patella

• kneecap• anterior surface of knee• flat sesmoid bone located in a tendon

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Tibia

• shin bone• medial to fibula• condyles• tibial tuberosity• anterior crest• medial malleolus

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Fibula

Insert figure 7.54

• lateral to tibia• long, slender• head• lateral malleolus• does not bear any body weight

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Ankle and Foot

• Tarsals (14)• calcaneus• talus• navicular• cuboid• lateral cuneiform• intermediate cuneiform• medial cuneiform

• Metatarsals (10)

• Phalanges (28)• proximal• middle• distal

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Ankle and Foot

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Clinical ApplicationTypes of Fractures

• green stick• fissured• comminuted• transverse• oblique• spiral

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Bone-Fractures• Classification-type-location-direction of the

fracture• Open/compound- broken through the skin

– Complication-infection-osteomyelitis-delayed union

Closed-not open to the outside of the skinDegree of the fracture-partial or complete break-

eg. Greenstick, seen in children, until age 10.Comminuted has more than two pieces and

compression fracture, involves two bones compressed together.

Impacted-fragments are wedged together-often breaks of the humerus

Bone Fractures

• Pattern-The direction of the injury produces a pattern of fracture.

• Transverse- angular forces• Spiral- results from a twisting motion• Location- Long bones, neck or head,

proximal/distal• Grouped according to their etiology

sudden trauma- most common

stress trauma- wear and tear on a bone

pathologic fractures- weakened by disease

Bone Healing

• Hematoma- Clot forms during the first 48/72 hrs after a fracture

• Cellular proliferation- Involves all three layers-

• Granulation tissue replace the clot

• New capillary buds and fibroblast

• Fibrocartilaginous callus forms distal to fracture- forming a bridge between the fragments

Bone healing

• Callus formation- cartilage forms at the site– 3/4 weeks mineral salts are deposited

• Ossification– Mature bone cells replace the callus, osteoclast

resorb the callus-cast removed at this point

• Remodeling- resorbition of excess callus fracture site becomes thicker and stronger in

relation to function