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Chapter 6-Skeletal System Functions 1. Support 2. Protect 3. Movement 4. Storage 5. Blood cell production
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Components of Skeletal System •
Bone
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Cartilage: reduce friction and model for bone formation
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Tendons: attach bone to muscle
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Ligaments: attach bone to bone
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Background Information • Bones, cartilage, tendons, and ligaments are connective tissues. • Proteoglycans: - large polysaccharides attached to proteins - part of ground substance - store water
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• Bone’s extracellular matrix is collagen and minerals (flexible and able to bear weight) • Cartilage’s extracellular matrix is collagen and proteoglycans (good shock absorber) • Tendons and ligaments’ extracellular matrix is collagen (very tough)
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Classification of Bones • Based on shape: long, short, flat, irregular • Type of bone tissue: compact and spongy (cancellous)
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Bone Shapes • Long: - Ex. Femur, tibia, fibula • Short: – Ex. Carpals, tarsals, phlanges
• Flat: – Ex. Ribs, sternum, skull
• Irregular: – Ex. Vertebrae and facial
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Long Bone Structures • Diaphysis: – shaft – compact bone tissue (on outside) • Epiphysis: – ends – spongy bone tissue • Articular cartilage: - covers epiphyses - reduces friction
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Articular cartilage Epiphysis Epiphyseal plates in juveniles
Spongy bone Compact bone Medullary cavity (contains red marrow in juveniles and yellow marrow in adults)
Diaphysis
Periosteum Endosteum
Young bone (a)
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• Epiphyseal plate: – site of growth – between diaphysis and epiphysis
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Articular cartilage Epiphysis
Epiphyseal lines in adults Spongy bone Compact bone
• Medullary cavity: – center of diaphysis – red or yellow marrow
Medullary cavity (contains red marrow in juveniles and yellow marrow in adults)
Diaphysis
Periosteum Endosteum
Adult bone (b)
• Periosteum: membrane around bone’s outer surface
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Articular cartilage Epiphysis Epiphyseal plates in juveniles
Spongy bone
• Endosteum: membrane that lines medullary cavity
Compact bone Medullary cavity (contains red marrow in juveniles and yellow marrow in adults)
Diaphysis
Periosteum Endosteum
Young bone (a)
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Articular cartilage Epiphysis Epiphyseal plates in juveniles Epiphyseal lines in adults Spongy bone Compact bone Medullary cavity (contains red marrow in juveniles and yellow marrow in adults)
Diaphysis
Diaphysis
Periosteum Endosteum
Young bone Adult bone (a)
(b)
Osteons (haversian systems)
Endosteum
Inner layer Periosteum Outer layer
Compact bone
Central canals Spongy bone with trabeculae
Connecting vessels
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Medullary cavity
(c)
Adult bone
Compact Bone Tissue • Location: outer part of diaphysis (long bones) and thinner surfaces of other bones
• Osteon: - structural unit of compact bone - includes lamella, lacunae, canaliculus, central canal, osteocytes
• Lamella: rings of bone matrix
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Osteons (haversian systems) Endosteum
Inner layer Periosteum Outer layer Compact bone
Central canals Spongy bone with trabeculae
Connecting vessels Medullary cavity (c)
Adult bone
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• Lacunae: spaces between lamella • Canaliculus: - tiny canals - transport nutrients and remove waste
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Osteons (haversian systems) Endosteum
Inner layer Periosteum Outer layer Compact bone
Central canals
• Central canal: - center of osteon - contains blood vessels
Spongy bone with trabeculae
Connecting vessels Medullary cavity (c)
Adult bone
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Osteon
Concentric rings of lamellae Central canal
Osteon
Lamellae on surface of bone Lamellae between osteons Periosteum Blood vessel within the periosteum Blood vessels connecting to a central canal Blood vessels within a central (Haversian) canal Canaliculi
LM 400x
(a)
Canaliculi Lacunae
(b) Blood vessel connecting to a central canal between osteons a: © Trent Stephens
Osteocytes in lacunae
Spongy Bone Tissue • Cancellous bone • Location: epiphyses of long bones and center of other bones • Trabeculae: interconnecting rods, spaces contain marrow • No osteons
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Bone Cells • Osteocytes: maintain bone matrix • Osteoblasts: build bone • Osteoclasts: carve bone 16
Bone Formation • Ossification: process of bone formation (occurs in utero) • Osteoblast’s role: - build bone - after an osteoblast becomes surrounded by bone matrix it becomes an osteocyte
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• Ossification center: where bone formation begins • Primary ossification center: - where bone 1st begins to appear - forms diaphyses • Secondary ossification center: forms epiphyses 18
Intramembranous Ossification • Bone formation within connective tissue membranes • Osteoblasts build bone • Ex. Skull bones
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Endochondral Ossification • Bone formation inside cartilage • Cartilage models are replaced by bone • Ex. All bones (except skull)
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Steps in Endochondral Ossification 1. Chondroblasts build a cartilage model, the chrondroblasts become chondrocytes. 2. Cartilage model calcifies (hardens). 3. Osteoblasts invade calcified cartilage and a primary ossification center forms diaphysis. 4. Secondary ossification centers form epiphysis. 5. Original cartilage model is almost completely ossified and remaining cartilage is articular cartilage. 22
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Femur Patella Epiphysis Epiphyseal plate Diaphysis (a) Length of bone increases.
1 Epiphyseal plate
Chondrocytes divide and enlarge.
2 3 Calcified cartilage is replaced by bone.
Bone of diaphysis (b)
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Epiphyseal side
1 New cartilage is produced on Thickness of the epiphyseal side epiphyseal of the plate as the plate remains chondrocytes divide unchanged. and form stacks of cells. 2 Chondrocytes mature and Bone is enlarge. added to diaphysis. 3 Matrix is calcified, and chondrocytes die. 4 The cartilage on the diaphyseal side of the plate is replaced by bone.
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2
3 4 LM 400x
Diaphyseal side (c)
(a): © Ed Reschke/Peter Arnold, Inc./ Photolibrary.com; (c): © Bio-Photo Assocs/Photo Researchers, Inc.
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Bone Growth • Infancy and youth: - long bones lengthen at epiphyseal plate - long bones widen by adding more lamella • End of bone growth (in length): epiphyseal plate is replaced by an epiphyseal line
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Figure 6.2b
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Bone Remodeling • What is it? - removal of existing bone by osteoclasts and deposition of new bone by osteoblasts - occurs in all bones - responsible for changes in bone shape, bone repair, adjustment of bone to stress, and calcium ion regulation 28
Bone Repair 1. Broken bone causes bleeding and a blood clot forms. 2. Callus forms which is a fibrous network between 2 fragments. 3. Cartilage model forms first then, osteoblasts enter the callus and form cancellous bone this continues for 4-6 weeks after injury. 4. Cancellous bone is slowly remodeled to form compact and cancellous bone. 29
Bone and Calcium Homeostasis • Bone is a major storage site for calcium • Movement of calcium in and out of bone helps determine blood levels of calcium • Calcium moves into bone as osteoblasts build new bone • Calcium move out of bone as osteoclasts break down bone • Calcium homeostasis is maintained by parathyroid hormone (PTH) and calcitonin 31
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Decreased blood Ca2+
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Increased blood Ca2+
Posterior aspect of thyroid gland
Kidney
Parathyroid glands
1 Decreased blood Ca2+ stimulates PTH secretion from parathyroid glands.
Thyroid gland
2 PTH stimulates osteoclasts to break down bone and release Ca2+ into the blood. 3 In the kidneys, PTH increases Ca 2+ reabsorption from the urine. PTH also stimulates active Vitamin D formation.
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PTH 2 Stimulates osteoclasts
Vitamin D
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Bone Osteoclasts promote Ca2+ Ca2+ uptake from bone.
Calcitonin 6 Inhibits osteoclasts
4 Vitamin D promotes Ca2+ absorption from the small intestine into the blood. 5 Increased blood Ca2+ stimulates calcitonin secretion from the thyroid gland. 6 Calcitonin inhibits osteoclasts, which allows for enhanced osteoblast uptake of Ca2+ from the blood to deposit into bone.
Osteoblasts promote Ca2+ deposition in bone.
Small intestine Ca2+
Blood
Hematopoietic Tissue • What is it? tissue that makes blood cells • Red marrow: location of blood forming cells • Yellow marrow: mostly fat 33
• Location of hematopoietic tissue in newborns: most bones (red marrow)
• Location of hematopoietic tissue in adults: - red is replaced with yellow marrow - red marrow is mainly in epiphyses of femur and humerus
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Bone Anatomy
• Foramen: - hole - Ex. Foramen magnum • Fossa: - depression - Ex. Glenoid fossa • Process: - projection - Ex. Mastoid process
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• Condyle: - smooth, rounded end - Ex. Occipital condyle • Meatus: - canal-like passageway - Ex. External auditory meatus • Tubercle: - lump of bone - Ex. Greater tubercle 36
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Axial Skeleton • Mastoid process: attached to neck muscles • External auditory meatus: ear canal • Nasolacrimal canal: - canal between nasal cavity and eye - conducts tears 38
• Styloid process: attachment site for tongue • Mandibular fossa: depression where lower jaw and skull meet • Glenoid fossa: where humerus meets scapula 39
• Hard palate: roof of mouth
• Foramen magnum: hole where spinal cord joins brainstem
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• Zygomatic: cheek bone • Mandible: lower jaw • Maxilla: upper jaw 41
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Incisive fossa Maxilla Palatine process of maxillary bone Horizontal plate of palatine bone
Inferior orbital fissure
Zygomatic bone Sphenoid bone
Vomer
Foramen ovale Foramen spinosum
Styloid process Mandibular fossa
External auditory canal Jugular foramen
Carotid canal
Occipital condyle
Mastoid process
Foramen magnum
Temporal bone
Occipital bone
Nuchal lines
Inferior view
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Hard palate
Vertebral Column • • • • • •
7 cervical vertebra 12 thoracic vertebra 5 lumbar vertebra 1 sacrum 1 coccyx Atlas: - 1st vertebra - holds head • Axis: - 2nd vertebra - rotates head 46
Functions of Vertebral Column • Support • Protect spinal cord • Movement
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Thoracic Cage • Protects vital organs • 12 pair of ribs • Sternum: breastbone • True ribs: attach directly to sternum by cartilage • False ribs: attach indirectly to sternum by cartilage • Floating ribs: not attached to sternum
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Pectoral Girdle • Scapula: shoulder blade • Clavicle: collar bone
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Upper Limb Bones • Humerus: upper limb • Ulna: forearm • Radius: forearm • Carpals: wrist • Metacarpals: hand
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Pelvic Girdle • Where lower limbs attach to body • Pelvis: includes pelvic girdle and coccyx • Ischium: inferior and posterior region • Ilium: most superior region • Acetabulum: hip socket (joint)
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Iliac crest Articular surface (area of articulation with sacrum)
Ilium Iliac fossa
Pelvic brim
Greater sciatic notch
Acetabulum
Ischium
Greater sciatic notch
Pubis
Ischial spine
Ischial spine Ischium
Pubic symphysis Obturator foramen
Ischial tuberosity (a)
Lateral view
(b)
Medial view
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Lower Limb Bones • Femur: thigh • Patella: knee cap • Tibia: large lower leg • Fibula: small lower leg 65
• Tarsals: ankle • Metatarsals: foot • Phalanges: toes and fingers
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Head
Head
Greater trochanter
Greater trochanter
Neck
Neck Lesser trochanter
Linea aspera
Body (shaft) of femur
Medial epicondyle Lateral epicondyle Intercondylar fossa
Lateral epicondyle
Patellar groove (a)
(b)
Lateral condyle
Medial condyle Anterior view
Posterior view
Anterior surface
68 Anterior view
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Articulations • What are they? where 2 bones come together (joint) • Synarthrosis: - nonmovable joint - Ex. skull • Amphiarthrosis: - slightly movable joint - Ex. Between vertebrae • Diarthrosis: - freely movable joint - Ex. knee, elbow, wrist
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Parietal bone Frontal bone
Squamous suture
Coronal suture
Occipital bone Lambdoid suture Mastoid (posterolateral) fontanel
Sphenoidal (anterolateral) fontanel Temporal bone
(a)
Lateral view
Frontal bones (not yet fused into a single bone)
Frontal (anterior) fontanel
Parietal bone
Sagittal suture
Occipital (posterior) fontanel
Occipital bone (b)
Superior view
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Bone
Synovial membrane Blood vessel Nerve
Fibrous part of joint capsule
Joint capsule
Bursa
Joint cavity (filled with synovial fluid) Articular cartilage
Tendon sheath Tendon
Outer layer
Bone
Inner layer
Periosteum
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class and Example of Joint
Structures Joined
Movement
Plane Acromioclavicular Carpometacarpal
Acromion process of scapula and clavicle Carpals and metacarpals 2–5
Slight Multiple axes as a group Slight Slight Slight Slight Slight
Costovertebral Intercarpal Intermetatarsal Intertarsal Intervertebral
Ribs and vertebrae Between carpal bones Between metatarsal bones Between tarsal bones Between articular processes of adjacent vertebrae
Sacroiliac
Between sacrum and coxal bone (complex joint with several planes and synchondroses)
Slight
Tarsometatarsal
Tarsal bones and metatarsal bones
Slight
Carpal and metacarpal of thumb Between carpal bones Manubrium of sternum and clavicle
Two axes
Hinge Cubital (elbow) Knee Interphalangeal Talocrural (ankle)
Humerus, ulna, and radius Femur and tibia Between phalanges Talus, tibia, and fibula
One axis One axis One axis Multiple axes; one predominates
Pivot Medial atlantoaxial Proximal radioulnar Distal radioulnar
Atlas and axis Radius and ulna Radius and ulna
Rotation Rotation Rotation
Ball-and-Socket Coxal (hip) Humeral (shoulder)
Coxal bone and femur Scapula and humerus
Multiple axes Multiple axes
Two axes Two axes
Metatarsophalangeal (ball of foot)
Atlas and occipital bone Metacarpal bones and phalanges Metatarsal bones and phalanges
Radiocarpal (wrist) Temporomandibular
Radius and carpal bones Mandible and temporal bone
Multiple axes Multiple axes; one predominates
Plane
Saddle Carpometacarpal pollicis Intercarpal Sternoclavicular
Slight Slight
Saddle
Hinge
Pivot
Ball-and-socket
Ellipsoid Atlantooccipital Metacarpophalangeal (knuckles)
Ellipsoid
Two axes
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Types of Movement • • • • •
Flexion: bending Extension: straightening Abduction: movement away from midline Adduction: movement toward the midline Pronation: rotation of the forearm with palms down • Supination: rotation of the forearm with palms up • Rotation: movement of a structure about the long axis 76
Effects of Aging on the Skeletal System and Joints 1. Decrease Collagen Production 2. Loss of Bone Density 3. Degenerative Changes
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