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Skeletal System

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Greg Horesovsky

on 13 September 2013

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Transcript of Skeletal System

Skeletal System Normal bone growth and maintenance require nutritional and hormonal factors
A dietary source of calcium and phosphate salts:
Plus small amounts of magnesium, fluoride, iron, and manganese
The hormone calcitriol:
Is made in the kidneys
Helps absorb calcium and phosphorus from digestive tract
Synthesis requires vitamin D3 (cholecalciferol) Requirements for Normal Bone Growth Bone Development
Human bones grow until about age 25
Osteogenesis:
Bone formation
Ossification:
The process of replacing other tissues with bone
Intramembranous Ossification
Begins deep in the dermis with development of osteoblasts
Produces flat bones of the skull and the mandible (lower jaw) and clavicle (collarbone)
Endochondral Ossification
Ossifies bones that originate as hyaline cartilage
Most bones originate as hyaline cartilage
There are six main steps in endochondral ossification Bone Formation and Growth Osteocytes
Mature bone cells that maintain the bone matrix
Live in lacunae
Are between layers (lamellae) of matrix
Connect by cytoplasmic extensions through canaliculi in lamellae
Do not divide
Functions:
To maintain protein and mineral content of matrix
To help repair damaged bone Compact and Spongy Bone The Structure of Spongy Bone
Does not have osteons
The matrix forms an open network of trabeculae
Trabeculae have no blood vessels
The space between trabeculae is filled with red bone marrow:
Which has blood vessels
Forms red blood cells
And supplies nutrients to osteocytes
Yellow marrow
In some bones, spongy bone holds yellow bone marrow
Is yellow because it stores fat Compact and Spongy Bone Bones are classified by
Shape
Internal tissue organization
Bone markings (surface features; marks) Classification of Bones Skeletal system includes
Bones of the skeleton
Cartilages, ligaments, and connective tissues
Functions of the Skeletal System:
Support
Storage of minerals (calcium) and lipids (yellow marrow)
Blood cell production (red marrow)
Protection
Leverage (force of motion) An Introduction to the Skeletal System Bones become thinner and weaker with age
Osteopenia begins between ages 30 and 40
Women lose 8% of bone mass per decade, men 3%
Osteoporosis
Severe bone loss
Affects normal function
Over age 45, occurs in:
29% of women
18% of men Osteopenia Parathyroid Hormone (PTH)
Produced by parathyroid glands in neck
Increases calcium ion levels by:
Stimulating osteoclasts
Increasing intestinal absorption of calcium
Decreasing calcium excretion at kidneys
Calcitonin
Secreted by C cells (parafollicular cells) in thyroid
Decreases calcium ion levels by:
Inhibiting osteoclast activity
Increasing calcium excretion at kidneys The Skeleton as a Calcium Reserve Bones store calcium and other minerals
Calcium is the most abundant mineral in the body
Calcium ions are vital to:
Membranes
Neurons
Muscle cells, especially heart cells The Skeleton as a Calcium Reserve Process of Remodeling
The adult skeleton:
Maintains itself
Replaces mineral reserves
Recycles and renews bone matrix
Involves osteocytes, osteoblasts, and osteoclasts
Bone continually remodels, recycles, and replaces
Turnover rate varies:
If deposition is greater than removal, bones get stronger
If removal is faster than replacement, bones get weaker Requirements for Normal Bone Growth Ossification Osteoclasts
Secrete acids and protein-digesting enzymes
Giant, multinucleate cells
Dissolve bone matrix and release stored minerals (osteolysis)
Are derived from stem cells that produce macrophages
Osteoblasts
Immature bone cells that secrete matrix compounds (osteogenesis)
Osteoid — matrix produced by osteoblasts but not yet calcified to form bone
Osteoblasts surrounded by bone become osteocytes Compact and Spongy Bone Cells in Bone
Make up only 2% of bone mass
Bone contains three types of cells:
Osteocytes
Osteoblasts
Osteoclasts Compact and Spongy Bone






Figure 6-3a Compact and Spongy Bone The Structure of Compact Bone
Osteon is the basic unit:
Osteocytes are arranged in concentric lamellae
Around a central canal containing blood vessels
Perforating canals:
perpendicular to the central canal
carry blood vessels into bone and marrow Compact and Spongy Bone Diaphysis
The shaft
A heavy wall of compact bone, or dense bone
A central space called medullary (marrow) cavity
Epiphysis
Wide part at each end
Articulation with other bones
Mostly spongy (cancellous) bone
Covered with compact bone (cortex) Structure of a Long Bone






Figure 6-5 Endochondral Ossification Shapes of Bones Phalanges of the foot
Phalanges:
14 bones of the toes
Hallux:
Big toe or great toe, two phalanges (distal, proximal)
Other four toes:
Three phalanges (distal, medial, proximal) The Lower Limbs Functions of the lower limbs
Weight bearing
Motion

Note: leg = lower leg; thigh = upper leg The Lower Limbs Made up of two hip bones (coxal bones)
Strong to bear body weight, stress of movement
Part of the pelvis
Coxal bones
Made up of three fused bones:
Ilium (articulates with sacrum)
Ischium
Pubis
The acetabulum:
Also called the hip socket
Is the meeting point of the ilium, ischium, and pubis
Is on the lateral surface of the hip bone (coxal bone) The Pelvic Girdle Bones of the Wrist and Hand Eight carpal bones
Four proximal carpal bones
Four distal carpal bones
Allow wrist to bend and twist
Metacarpal Bones
The five long bones of the hand
Numbered I–V from lateral (thumb) to medial
Articulate with proximal phalanges
Phalanges of the Hands (14 Total Finger Bones)
Pollex (thumb):
Two phalanges (proximal, distal)
Fingers:
Three phalanges (proximal, middle, distal) The Upper Limbs Also called the shoulder girdle
Connects the arms to the body
Positions the shoulders
Provides a base for arm movement
Consists of
Two clavicles
Two scapulae
Connects with the axial skeleton only at the manubrium The Pectoral Girdle Ribs 1–7 (true ribs)
Vertebrosternal ribs
Connected to the sternum by costal cartilages
Ribs 8–12 (false ribs)
Do not attach directly to the sternum
Vertebrochondral ribs (ribs 8–10):
Fuse together
Merge with cartilage before reaching the sternum
Floating or vertebral ribs (ribs 11–12):
Connect only to the vertebrae and back muscles
Have no connection with the sternum The Thoracic Cage The Thoracic Cage Spinal Curvature
Thoracic and sacral curves:
Are called primary curves (present during fetal development)
Or accommodation curves (accommodate internal organs)
Lumbar and cervical curves:
Are called secondary curves (appear after birth)
Or compensation curves (shift body weight for upright posture) The Vertebral Column The Spine or Vertebral Column
Protects the spinal cord
Supports the head and body
26 bones:
24 vertebrae, the sacrum, and the coccyx The Vertebral Column The Frontal Bone
Functions of the frontal bone:
Forms the anterior cranium and upper eye sockets
Contains frontal sinuses
The Parietal Bones
Function of the parietal bones:
Forms part of the superior and lateral surfaces of the cranium
The Occipital Bone
Function of the occipital bone:
Forms the posterior and inferior surfaces of the cranium
The Temporal Bones
Functions of the temporal bones:
Surround and protect inner ear
Attach muscles of jaws and head The Cranial Bones of the Skull Cranial Bones
Enclose the cranial cavity
Which contains the brain:
And its fluids, blood vessels, nerves, and membranes
Facial Bones
Superficial facial bones:
For muscle attachment
Deep facial bones:
Separate the oral and nasal cavities
Form the nasal septum The Skull Bones of the Ankle and Foot Bones of the Ankle and Foot The Ankle
Also called the tarsus:
Consists of seven tarsal bones
Bones of the ankle:
Talus:
carries weight from tibia across trochlea
Calcaneus (heel bone):
transfers weight from talus to ground
attaches calcaneal (Achilles) tendon
Metatarsal Bones of the Foot
Five long bones of foot
Numbered I–V, medial to lateral
Articulate with toes The Lower Limbs The Tibia
Also called the shinbone
Supports body weight
Larger than fibula
Medial to fibula
The Fibula
Attaches muscles of feet and toes
Smaller than tibia
Lateral to tibia The Lower Limbs The Patella
Also called the kneecap
Formed within tendon of quadriceps femoris ( a group of muscles that strengthens the knee) The Lower Limbs Bones of the Lower Limbs
Femur (thigh)
Patella (kneecap)
Tibia and fibula (leg)
Tarsals (ankle)
Metatarsals (foot)
Phalanges (toes) The Lower Limbs The Humerus
Also called the arm
The long, upper arm bone
Articulates with the pelvic girdle The Upper Limbs The upper limbs consist of the arms, forearms, wrists, and hands

Note: arm (brachium) = 1 bone, the humerus The Upper Limbs Forms mainly the extremities of the body and their connections to the axial skeleton

Consists of:
Limbs (arms and legs)
Pectoral Girdle (clavicles and scapulas)
Pelvic Girdle (ilium, ischium and the pubis) The Appendicular Skeleton The Sternum
A flat bone
In the midline of the thoracic wall
Three parts of the sternum:
The manubrium
The sternal body
The xiphoid process The Thoracic Cage The Skeleton of the Chest
Supports the thoracic cavity:
Consists of:
thoracic vertebrae
ribs
sternum (breastbone)
The Rib Cage
Formed of ribs and sternum
Functions of the Thoracic Cage
Protects organs of the thoracic cavity:
Heart, lungs, and thymus
Attaches muscles:
For respiration
Of the vertebral column
Of the pectoral girdle
Of the upper limbs The Thoracic Cage






Figure 6-19 The Sacrum and Coccyx






Figure 6-17a The Cervical Vertebrae The Sphenoid
Functions of the sphenoid:
Part of the floor of the cranium
Unites cranial and facial bones
Strengthens sides of the skull
The Ethmoid
Functions of the ethmoid:
Forms anteromedial floor of the cranium
Roof of the nasal cavity
Part of the nasal septum and medial orbital wall
Contains ethmoidal air cells (network of sinuses) The Cranial Bones of the Skull The Femur The Pelvis The Forearm (also called the Antebrachium)
Consists of two long bones:
Ulna (medial)
Radius (lateral) The Upper Limbs The Scapulae
Also called shoulder blades
Broad, flat triangles
Articulate with arm and collarbone
Anterior surface: the subscapular fossa The Pectoral Girdle The Clavicles
Also called collarbones
Long, S-shaped bones
Originate at the manubrium (sternal end)
Articulate with the scapulae (acromial end) The Pectoral Girdle Atlas- First cervical vertebra

Axis – second cervical vertebra

The spinal chord runs down the canal formed by the vertebra being stacked on top of one another.

Intervertebral Discs are found between each vertebra and keep the spine flexible and provide cushioning and absorb shock

Coccyx is the remnant of a tail The Atlas and Axis Vertebral column
Divided into 5 main regions
Cervical Spine (7)
Thoracic Spine (12)
Lumbar Spine (5)
Sacrum (5 fused vertebrae)
Coccyx (4 fused vertebrae)

The 5 Sacrum vertebrae and the 4 Coccyx vertebrae are fused to form one bone

Vertebrae are numbered from top down
C1-C7
T1-T12
L1-L5 The Vertebral Column The Hyoid Bone
Functions of the hyoid bone:
Supports the larynx
Attaches muscles of the larynx, pharynx, and tongue The Facial Bones of the Skull
There are 8 Cranial Bones:
Frontal
Parietal (2)
Occipital
Temporal(2)
Sphenoid
Ethmoid The Cranial Bones The Axial Skeleton
Forms the longitudinal axis of the body
Has 80 bones:
The skull:
eight cranial bones
fourteen facial bones
Bones associated with the skull:
six auditory ossicles
the hyoid bone
The Appendicular Skeleton
126 bones
Allows us to move and manipulate objects
Includes all bones besides axial skeleton:
The limbs
The supportive girdles Skeletal Divisions The Skeleton Maxilla (2) upper jaw
Mandible (1) Lower jaw bone
Mandible is the only moveable facial bone
Nasal (5)
Lacrimal (2) contain tear ducts
Zygomatic (2) cheek bones The Bones of the Face Gliding Joints
Flattened or slightly curved faces
Limited motion (nonaxial)
End of clavicles, between carpals and tarsals
Hinge Joints
Angular motion in a single plane (monaxial)
Between occipital bone and atlas, elbow, knee, ankle
Pivot Joints
Rotation only (monaxial)
Rotation of the head, pronantion and supination of the ulna A Structural Classification of Synovial Joints Functional Classifications
Synarthrosis (immovable joint):
No movement
Fibrous or cartilaginous connections
May fuse over time
Amphiarthrosis (slightly movable joint):
Little movement
Fibrous or cartilaginous connections
Diarthrosis (freely movable joint):
More movement
Also called synovial joints
Subdivided by type of motion Classification of Joints Ellipsoid Joints
Oval articular face within a depression
Motion in two planes (biaxial)
Between radius and carpals, in the phalanges
Saddle Joints
Two concave, straddled (biaxial)
thumbs
Ball-and-Socket Joints
Round articular face in a depression (triaxial)
Permits all combinations of movement
Shoulder and hip joints A Structural Classification of Synovial Joints A Structural Classification of Synovial Joints
Gliding
Hinge
Pivot
Ellipsoid
Saddle
Ball-and-socket A Structural Classification of Synovial Joints Types of Movements Special Movements
Opposition:
Thumb movement toward fingers or palm (grasping)
Protraction:
Moves anteriorly
In the horizontal plane (pushing forward)
Retraction:
Opposite of protraction
Moving anteriorly (pulling back)
Elevation:
Moves in superior direction (up)
Depression:
Moves in inferior direction (down) Types of Movements Special movements
Inversion:
Twists sole of foot medially
Eversion:
Twists sole of foot laterally
Dorsiflexion:
Flexion at ankle (lifting toes)
Plantar flexion:
Extension at ankle (pointing toes) Types of Movements Rotation
Pronation:
Rotates forearm, radius over ulna
Supination:
Forearm in anatomical position Types of Movements Types of Movements Rotation
Direction of rotation from anatomical position
Relative to longitudinal axis of body
Left or right rotation
Medial rotation (inward rotation):
Rotates toward axis
Lateral rotation (outward rotation):
Rotates away from axis Types of Movements Angular Motion
Circumduction:
Circular motion without rotation
Angular motion Types of Movements Types of Movements Types of Movements Angular Motion
Abduction:
Angular motion
Frontal plane
Moves away from longitudinal axis
Adduction:
Angular motion
Frontal plane
Moves toward longitudinal axis Types of Movements Articulations
Body movement occurs at joints (articulations) where two bones connect
Joint Structure
Determines direction and distance of movement (range of motion)
Joint strength decreases as mobility increases An Introduction to Articulations






Figure 6-34 Types of Movements Types of Movements Angular Motion
Flexion:
Angular motion
Anterior–posterior plane
Reduces angle between elements
Extension:
Angular motion
Anterior–posterior plane
Increases angle between elements
Hyperextension:
Angular motion
Extension past anatomical position Types of Movements Diarthrosis: Synovial Joints Synovial joints provide a wide range of movement and are typically found at the ends of long bones.

Additional padding in the form of fibrocartilage pads or Menisci (meniscus) are present in the knee.

Where a tendon or a ligament rubs against other tissues, bursae (bursa) form to reduce friction and act as shock absorbers.
Bursae are small packets of connective tissue containing synovial fluid A Structural Classification of Synovial Joints Bone Anatomy Bone Physiology Joints and Movement
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