SKELETAL SYSTEM

Chapter

7

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Chapter 7Skeletal System

Bone Classification

• Long Bones• Short Bones• Flat Bones• Irregular Bones• Sesamoid Bones (round)

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Bone Function

• Support and Protection• gives shape to head, etc.• supports body’s weight• protects lungs, etc.

• Body Movement• interacts with muscles• bones act as rigid bar of a lever

• Blood Cell Formation• hematopoiesis• red marrow

• Inorganic Salt Storage• calcium • phosphate• magnesium• sodium• potassium

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Parts of a Long Bone• epiphysis (end)

• distal• proximal

• diaphysis (shaft)• compact bone• spongy bone

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• medullary cavity (central space)

• marrow• red (hematopoiesis, make RBC’s)• yellow (fat storage)

• articular cartilage• periosteum (outer covering)

• endosteum (inner covering)

Compact and Spongy Bone

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Microscopic Structureof Compact Bone

• osteon (cells grow in circle)

• osteonic canal (canal for bv)

• perforating canal (for bv)

• osteocyte (bone cell)

• lacuna (space)

• bone matrix (collagen, salt)

• canaliculus (connects cells)

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Bone Development

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

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

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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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Terms Used to Describe Skeletal Structures

• See table 7.4 on page 202

• These terms will be used to describe specific parts of a bone.

• You will need to understand what many of them mean.

Hyoid (1)

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• Supports tongue

Skull

Frontal (1) (orange)

• forehead• roof of nasal cavity• roofs of orbits• frontal sinuses• supraorbital foramen• coronal suture

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Skull

Parietal (2) (blue)

• side walls of cranium• roof of cranium• sagittal suture

•between 2 parietal bones

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Skull

Temporal (2) (red)

• 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) (blue)

• back of skull• base of cranium• foramen magnum• occipital condyles• lambdoidal suture

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Skull

Sphenoid (1) (purple)

• 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

•Support mucous membranes•moisten and warm air

• ethmoidal sinuses• crista gallis

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Facial Skeleton

Maxilla (2) (yellow)

• 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) (Green)

• prominences of cheeks• lateral walls of orbits• floors of orbits• temporal process

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Facial Skeleton

Lacrimal (2) (blue)

• medial walls of orbits• groove from orbit to nasal cavity

•pathway for tears

Nasal (2) (green)

• bridge of nose

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Facial Skeleton

Vomer (1) (fuscia)

• inferior portion of nasal septum

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Facial Skeleton

Inferior Nasal Conchae (2) (blue)

• extend from lateral walls of nasal cavity

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Facial Skeleton

Mandible (1)• lower jaw• only mobile bone in skull• body• ramus• mandibular condyle• coronoid process• alveolar process• mandibular foramen• mental foramen

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Infantile Skull

Fontanels – fibrous membranes (soft spot)

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Fontanels close by:

Posterior – 2 mo

sphenoid – 3 mo

Mastoid – end 1st yr

Anterior – end 2nd yr

Vertebral Column

• cervical vertebrae (7)• thoracic vertebrae (12)• lumbar vertebrae (5)• sacrum (1; 5 fused)• coccyx (1; 4 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 (7)

• Atlas – 1st; supports head• Axis – 2nd; dens pivots to turn head• transverse foramina• bifid spinous processes• vertebral prominens – useful landmark on 7th

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Thoracic Vertebrae (12)

• long spinous processes• rib facets

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Lumbar Vertebrae (5)

• large bodies• thick, short spinous processes

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Sacrum (1)

• five fused vertebrae (between 18 – 30 yrs)• median sacral crest• dorsal sacral foramina• posterior wall of pelvic girdle• sacral promontory

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Coccyx (1)

• tailbone• four fused vertebrae (by 25 yrs)

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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 (24)

• True ribs (7)[on each side]• False ribs (5)[on each side]

• floating (inferior 2) [on each side]

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Rib Structure

• Shaft• Head – posterior end; articulates with vertebrae• Tubercle – articulates with vertebrae• Costal cartilage – hyaline cartilage, connect rib to sternum

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Sternum (1)

• Manubrium• Body• Xiphoid process

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Pectoral Girdle

• shoulder girdle • clavicles (2)• scapulae (2)• supports upper limbs

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Clavicles (2)

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

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Scapulae (2)

• 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 (2)

•bone in upper arm• head• greater tubercle• lesser tubercle• anatomical neck• surgical neck• deltoid tuberosity• capitulum (w/ radius)• trochlea (w/ ulna)• coronoid fossa• olecranon fossa

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Radius (2)

• lateral forearm bone• head

•allows rotation•crosses over ulna

• radial tuberosity• styloid process

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Ulna (2)

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

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Wrist and Hand

• Carpals (16) [8 in each]• trapezium• trapezoid• capitate• scaphoid• pisiform• triquetrum• hamate• lunate

• Metacarpals (10) [5 in each]

• Phalanges (28) [14 in each]• proximal phalanx• middle phalanx• distal phalanx

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Pelvic Girdle

• Coxae (2)• supports trunk of body• protects viscera• Sacrum and Coccyx

•sometimes considered part of girdle

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Coxae (2)

• 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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Male and Female Pelvis

Female• iliac bones more flared• broader hips• pubic arch angle greater• more distance between ischial spine and ischial tuberosity

• pelvic brim wider• 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 (2)

• longest/strongest bone• head• fovea capitis• neck• greater trochanter• lesser trochanter• linea aspera• condyles• epicondyles

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Patella (2)

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

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Tibia (2)

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

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Fibula (2)

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) [7 in each]• calcaneus• talus• navicular• cuboid• lateral cuneiform• intermediate cuneiform• medial cuneiform

• Metatarsals (10) [5 in each]

• Phalanges (28) [14 in each]• proximal• middle• distal

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Ankle and Foot

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Life-Span Changes

• decrease in height at about age 30• calcium levels fall• bones become brittle• osteoclasts outnumber osteoblasts• spongy bone weakens before compact bone• bone loss rapid in menopausal women• hip fractures common• vertebral compression fractures common

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Clinical Application

Types of Fractures

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

•open

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