Chapter 7
Skeletal System
Key Points
 Macro/microscopic structure of bone
 Development of bones
 Homeostasis of bones
 Function of skeletal system
 Adult vs. infant skull
 Comparison of joint types
 Types of joint movements
Bone Types
 Long bones - longer than wide
 Short bones - cube-like
 Flat bones  Irregular bones - variety of shapes
 Sesamoind - embedded in connective
tissue
Anatomy of a Long Bone
 Epiphysis - ends
 Articular cartilage (hyaline)
 Diaphysis – shaft of the bone
 Periosteum - tough, vascular tissue
 Process - bony projections
 Why useful?
Internal Anatomy of a Long Bone
 compact bone - tightly packed tissue found
in diaphysis
 Why useful?
 spongy bone - branching bony plates
found in epiphysis
 Purpose?
 Medullary cavity - hollow tubelike chamber
in the diaphysis
Internal Anatomy of a Long Bone
 Endosteum lines medullary cavity
 marrow fill the medullary cavity
 red - blood cell production
 yellow - stores fat
Microscopic Structure
 osteocytes arranged around the osteonic
canal (osteon)
 purpose of canals?
 Nutrients diffuse through the osteocytes
Bone Development and Growth
 bone forms by replacing connective tissue
 intramembranous bone
 Sheet-like layers
 endochondral bones
 Masses of cartilage then replaced by bone
tissue
 Two types of bone cells
 osteoblasts
 osteoclasts
Growth of an Endochondral Bone
 Replacement of cartilage begins in the
primary ossification center
 Development continues outward
 Later, secondary ossification sites
appear in epiphysis
 These sites are called epiphyseal
plates.
Growth of an Endochondral Bone
 osteoclasts break down calcified
osteocytes
 This eroding process forms medullary
cavity
Bone functions
 What are they?
 Shape, support, and protect
 movement
 blood cell production
 storage of inorganic salts
Support and protection
 Shape – example?
 Face
 Support – example?
 Entire skeleton
 Protection – example?
 Rib cage & skull
Blood Cell Formation
 Hematopoiesis – the process of forming
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blood cells
Starts early in the embryo stage of
development (not always in bone marrow)
As body develops production switches to
liver and spleen
Then manufactured in marrow
Marrow is considered a soft mass of
connective tissue
Hematopoiesis
 Red marrow produces erythrocytes,
leukocytes, and thrombocytes
 Which is red, white, or platelets?
 Red color is due to hemoglobin
 Infants have mostly red marrow
 Why would this be?
 As aging occurs, red marrow is replaced
with yellow marrow
Hematopoiesis
 Red marrow locations within adults: skull,
ribs, sternum, clavicle, vertebrae, pelvis
Storage of salts
 Salts account for about 70% of bone
matrix
 When blood calcium levels are low
hormones stimulate osteoclasts to break
down bone tissue
 What role does calcium play in the body?
 Why would they do this?
 High concentrations of salt stimulates
osteoblasts to form bone
Osteoporosis
 The loss of bone volume
 Bones develop large spaces and canals
that fill with fibrous and fatty tissue
 What would this cause?
 Lack of bone strength
 Why would lack of calcium increase risk?
Homeostasis of Bone
 What is homeostasis?
 Bone is continually resorbed and deposited to
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keep bone mass constant
Resorption cells - osteoclasts
Replacing cells – osteoblasts
Discuss:
nutrition, exposure to sunlight, hormones,
exercise
 effects on bones?
Skeleton
 Condyle – Rounded process, usually meets with
another bone
 Foramen – Opening through a bone
 Used for what?
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Suture – interlocking line between two bones
Sinus – Cavity within a bone
Process – Prominent projection of the bone
Facet – small, nearly flat surface
Table 7.2 on page 142
Repair Bone fractures
 Break causes vessels to rupture
 What does this cause?
 Spongy bone develops near new vessels;
fibrocartilage forms in more superficial
regions
 Cell types - osteoblasts
 Osteoclasts will remove bone fragments
 Cartilage will be replaced by a bony callus
Repair of fracture
 There is typically more bone produced at
site of healing
 Why would this be?
 How does the bone get back to normal?
 Osteoclasts will reshape to like original
bone
Types of fractures
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Greenstick –
incomplete, only one side of bone
Transverse –
Complete break to right angle to lengthwise of
long bone. Usually traumatic
Oblique Rare. Break at an angle
Comminuted –
More than two fragments broken off. traumatic
Types of fractures
Types of fractures
 Impacted –
 Occurs after a fall, vertebral column
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compressed, and cracks
Pathologic Disorder that weakens the bone, leading
to a fracture
Stress A bone becomes stressed from over use.
 Can cause slight breaks
Synovial Joints
 Joint capsule (ligaments) – Encloses the
joint.
 Synovial membrane – encloses the space
between bones, secretes synovial fluid
 What is this used for?
 Meniscus – shock absorbing articular
cartilage between bones
 Bursae – sac filled with synovial fluid.
Types of Joints
 5 types , table 7.4 page 165
 Ball and socket - ball shaped head and cup
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shaped cavity
Example – shoulder and hip
Condyloid - oval condyle and elliptical cavity,
movement in different planes
Example - metacarpophalangeal joint
Gliding - nearly flat surfaces, sliding and twisting
movements
Example – intertarsal joint
Joints
 Hinge - convex surface and concave
surface, movement in one plane
 Example – elbow, knee
 Pivot - cylindrical surface within a ring,
rotation around a central axis
 Example - radioulnar joint
Joint Movements
 Flexion – angle decreases (example?)
 Extension – angle increases (example?)
 Dorsiflexion – bending the foot toward shin
 Plantar flexion – bending foot toward sole
 Hyperextension – Extending joint past
anatomical position (example?)
 Abduction – moving away from midline
 Adduction – moving closer to midline
Joint Movements
 Pronation – turning hand so the palm is down
 Supination – turning the hand so the palm is
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up
Rotation – moving the part around an axis
Circumduction – moving a part in a circular
path
Elevation – raising a body part
Depression – lowering a body part
Assignment:
 Pg 172
 Review exercises
 Part A - #8 (do three examples) #13
 Part B – try to do it without your notes
 Critical thinking
 #1