Chapter 6 Flashcards
(124 cards)
1
Q
Skeletal System
A
Components include:
- Bones of the skeleton
- Cartilages, joints, ligaments, connective tissue that stabilize or connect bones
2
Q
Functions of the Skeletal System
A
- Support
-Provides structural support for the entire body
-Bones provide attachments for soft tissues and organs - Storage of minerals and lipids
-Mineral reserves for calcium and phosphorus ions held in calcium salts in bone
-Yellow bone marrow stores lipids for energy reserves - Blood cell production
-Red blood cells, white blood cells, and other blood elements produced in the red bone marrow - Protection
-Soft tissues and organs are surrounded by skeletal structures
Examples:
-The skull encloses the brain
-The ribs protect the heart and lungs - Leverage
-Bones function as levers
-Change size and direction of force generated by skeletal muscles
-Result is body movement
3
Q
Bone or osseous tissue
A
-Supporting connective tissue containing cells in a matrix
-Cells are called osteocytes
Matrix contains:
-Calcium salts in the form of calcium phosphate, Ca3(PO4)2
-Accounts for almost 2/3 of the weight of bone
Extracellular protein fibers
-About 1/3 of bone weight comes primarily from collagen fibers
4
Q
Classifying bones by shape
A
- Bones of the skeleton are categorized into four general shapes
1. Long bones - Longer than they are wide
2. Short bones - About as wide as they are long
3. Flat bones - Thin and relatively broad
4. Irregular bones - Complex shapes that don’t fit another category
5
Q
Features of a Long Bone
A
- The diaphysis is the central shaft
- Surrounds a marrow cavity, or medullary cavity, in the center filled with bone marrow
- The epiphyses are the expanded portions at each end
- Covered with articular cartilage
- Articulate with an adjacent bone at a joint
6
Q
Types of Bone Tissue in a Long Bone
A
- Compact bone, or dense bone
- Relatively solid
- Forms the wall of the diaphysis
- Spongy bone, or cancellous bone
- Interlacing network of bony rods separated by spaces
- Fills the epiphyses
- Lines the marrow cavity
7
Q
Coverings of a Long Bone
A
- Outer surface covered by periosteum
- Inner cellular layer
- Outer fibrous layer
- Isolates bone from surrounding tissue
- Forms attachments with fibers of tendons and ligaments
- Inner surfaces and spongy bone of marrow cavity covered by endosteum
- Functions during bone growth and repair
8
Q
Microscopic Features of Bone
A
- Bone cells are called osteocytes
- Located in pockets called lacunae
- Found between sheets of calcified matrix called lamellae
- Canaliculi are small channels
- Contain cytoplasmic extensions of the osteocytes
- Radiate through the matrix
- Connect the lacunae to blood vessels for nutrient and waste exchange
9
Q
Histology of Compact Bone
A
- Basic functional unit is the osteon, or Haversian system
- Osteocytes arranged in concentric layers (lamellae)
- Layers surround a central canal, or -Haversian canal
- Central canals run parallel to surface of bone and contain blood vessels
10
Q
Perforating canals
A
Link blood vessels of central canal with blood vessels of periosteum and marrow cavity
11
Q
Characteristics of Compact Bone
A
- Covers all bone surfaces except inside joint capsules
- Articular cartilage protects opposing bone surfaces here
- Parallel arrangement of osteons resists stress in specific direction
- Withstands forces applied on either end of a long bone
- Cannot tolerate moderate stress applied to the side of the shaft
12
Q
Structural Features of Spongy Bone
A
- Has no osteons
- Lamellae form rods or plates called trabeculae
- Still contains osteocytes, lacunae, and canaliculi
- Contains red bone marrow
- Found in spaces between trabeculae
13
Q
Functional Features of Spongy Bone
A
Found in:
-Locations not heavily stressed
-Locations with stresses arriving from many different directions
Example: epiphyses of long bones where stresses transferred across joints
-Much lighter than compact bone
-Reduces weight of the skeleton
-Easier for muscles to move bones
14
Q
Osteoblasts
A
Produce new bone through a process called ossification
15
Q
Osteocytes
A
- Most abundant cells in bone
- Mature cells that maintain bone structure by recycling calcium salts
16
Q
Osteoclasts
A
- Secrete acid and enzymes that dissolve the matrix
- Process releases minerals through osteolysis, or resorption
17
Q
Bone Formation
A
-Embryonic development of bone
-Begins at week 6 as a cartilaginous formation
-Replaced with bone, a process called ossification
Two types
1. Intramembranous ossification
2. Endochondral ossification
Calcification occurs during ossification
-Can also occur in other tissues besides bone
18
Q
Intramembranous Ossification
A
- Occurs during fetal development
- Bone develops within sheets of connective tissue
- Begins in an ossification center
- Osteoblasts differentiate from connective tissue stem cells and form new bone matrix
- Bone matrix formation extends outward
- Osteoblasts surrounded by matrix change into osteocytes
- Blood vessels grow into area and are trapped within developing bone
- Bone remodeling produces osteons of compact bone
- Flat bones of skull formed in this manner
19
Q
Endochondral Ossification
A
-Process of formation for most bones of the skeleton
-Begins with hyaline cartilage models
-Cartilage replaced by true bone in five steps
Steps 1–3 of Endochondral Ossification
1. Chondrocytes enlarge and surrounding matrix begins to calcify
-Chondrocytes die from lack of nutrients
Calcification of matrix slows diffusion
2. Bone formation starts at the shaft surface
-Blood vessels grow around edges
-Cells of perichondrium differentiate into osteoblasts
-Osteoblasts produce bone matrix around shaft surface
3. Blood vessels invade inner region of cartilage
-Migrating fibroblasts differentiate into osteoblasts
-New osteoblasts form spongy bone in center of shaft at the primary ossification center
-Bone develops toward each end filling shaft with spongy bone
4. Osteoclasts begin to break down spongy bone in center of bone
-Forms marrow cavity
-Epiphyseal cartilages, or epiphyseal plates, on the ends of the bone continue to enlarge
-Increases length of the bone
5. Centers of the epiphyses begin to calcify
-Secondary ossification centers form as blood vessels and osteoblasts enter
-Epiphyses fill with spongy bone
-Thin layer of original cartilage covers joint surfaces as the articular cartilage Bone of shaft and epiphysis separated by epiphyseal
20
Q
Epiphyseal Line
A
- At puberty, bone growth accelerates due to increased sex hormone production
- Osteoblasts produce bone faster than the epiphyseal cartilage can expand
- Epiphyseal cartilages get narrower until disappear
- Called epiphyseal closure
- X-rays of adult bones show former location of epiphyseal cartilage as epiphyseal line
21
Q
Appositional Growth
A
- Growth in diameter of bones occurs along with growth in length
- Process of growing in diameter is appositional growth
- Periosteum cells develop into osteoblasts
- Produce more matrix on the outer surface of the bone
- Osteoclasts erode the inner surface
- Marrow cavity enlarges as a result
22
Q
Timing of Epiphyseal Closure
A
- Varies from bone to bone
- Digits close early
- Arm, leg, and pelvis bones close later
- Varies from person to person
- Different timing in males versus females
- Mostly due to differences in sex hormones
- Later closure in males
23
Q
Requirements for Bone Growth (Mineral Supply)
A
- Calcium salts (calcium and phosphate)
- Absorbed from mother’s bloodstream during prenatal development
24
Q
Requirements for Bone Growth (Vitamin D3)
A
- Plays role in calcium metabolism
- Liver and kidney process into calcitriol that stimulates calcium and phosphate absorption
- Manufactured by epidermal cells exposed to UV radiation
- Also obtained from dietary supplements
- Deficiency leads to softening of bones
- Condition called osteomalacia in adults and rickets in children
25
Requirements for Bone Growth (Vitamin A and C)
- Provide support for osteoblasts
- Various hormones
- Growth hormone
- Thyroid hormone
- Sex hormones
- Calcium-balancing hormones
26
Bone Remodeling Process
- Remodeling process recycles and renews organic and mineral components of bone matrix
- Osteocytes maintain matrix, continually removing and replacing calcium salts
- Osteoclasts continually remove matrix
- Osteoblasts continually build matrix
- Normally activity is balanced
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Role of Bone Remodeling
- Turnover of minerals gives bone ability to adapt to new stresses
- Heavily stressed bones are thicker and stronger
- Regular exercise important to maintaining bone structure
- Bones receiving lower than normal stress are thinner and more brittle
- Inactivity (such as using crutches) results in loss of bone mass
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Rate of Bone Remodeling
- Rate of remodeling varies with age and type of bone
- In young adults, nearly 1/5 of the skeleton is recycled and replaced each year
- Spongy bone remodeled more frequently than compact
- Spongy bone in head of femur replaced 2–3 times per year
- Compact bone of femur shaft largely untouched
29
Skeleton as a Calcium Reserve
-Calcium is the most abundant mineral in the body
-99% of calcium is deposited in the skeleton
-Essential mineral for many physiological processes
Examples: neuron and muscle cell function
-Very close regulation required
-Small changes in calcium ion concentrations affect cellular function
-Larger changes can cause convulsions and death
-Calcium balance is regulated by:
Parathyroid hormone (PTH) and calcitriol to raise calcium levels
-Calcitonin to lower calcium levels in body fluids
30
Fracture Naming
- Fracture is a crack or break in a bone
- Two broad categories based on external appearance
- Closed (simple) fractures
- Completely internal (no break in the skin)
- Can be seen only on x-rays
- Open (compound) fractures
- Project through the skin
- More dangerous due to risk of infection
- Fractures also named by nature or location of the break
31
Four Steps to Repair Fractures
1. Large blood clot, or fracture hematoma, forms.
- Closes off the injured blood vessels
- Lack of blood flow kills osteocytes, resulting in dead bone extending on either side of the fracture
2. Cells of periosteum and endosteum divide and migrate into fracture area
- Internal callus of spongy bone unites inner edges of fracture
- External callus of cartilage and bone stabilizes outer edges of fracture
3. Osteoblasts replace cartilage with spongy bone
4. Spongy bone is replaced by compact bone
- Leaves slightly thicker spot at the fracture site
32
Osteopenia and Aging
Bones become thinner and weaker as normal part of aging
33
Osteopenia
- Inadequate ossification that naturally occurs as part of the aging process
- Begins between ages 30 and 40
- Osteoblast activity slows
- Osteoclast activity remains constant
- Women lose about 8% of skeletal mass each decade
- Men lose about 3% of skeletal mass each decade
34
Osteoporosis
- Loss of bone mass that impairs normal function and can lead to more fractures
- More severe than normal osteopenia
- Condition is more common in women
- Process accelerates after menopause
- Due to a decline in circulating estrogen
- Condition less common in men due to levels of androgens (male sex hormones)
- Causes increased bone fractures and decreased ability to repair
35
Bone Markings
- Landmark features on the surfaces of bones are called bone markings or surface features
- Elevations or projections
- Where tendons and ligaments attach
- Where bones articulate
- Depressions, grooves, and openings
- Where blood vessels and nerves pass through the bone
36
Skeletal Divisions
- Skeletal system consists of 206 bones
- Can be divided into two divisions
1. Axial skeleton
2. Appendicular skeleton
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Axial Skeleton
- Forms longitudinal axis of body
- Contains 80 bones subdivided into:
1. Skull bones (22)
2. The bones associated with the skull (6 auditory ossicles and the hyoid bone)
3. Bones of the thoracic cage (25)
4. Bones of the vertebral column (26)
38
Appendicular Skeleton
- Bones of the pectoral girdle and upper limbs
| - Bones of the pelvic girdle and lower limbs
39
Functions of the Axial Skeleton
- Creates framework for support and protection of the brain, spinal cord, and organs in the ventral body cavity
- Provides surface area for attachment of muscles that:
1. Move the head, neck, and trunk
2. Perform respiration
3. Stabilize elements of the appendicular skeleton
40
The Skull
-Protects the brain
-Houses brain and sense organs for sight, smell, taste, hearing, and balance
-Made up of 22 bones
8 form the cranium
-Encloses cranial cavity, chamber supporting the brain
-14 are facial bones
41
Bones Associated with the Skull
```
-Seven bones associated with the skull
6 auditory ossicles (ear bones)
-Encased by the temporal bone
-Involved with sound detection
-Hyoid bone
-Connected to inferior skull by pair of ligaments
```
42
The Frontal Bone
- Forms the forehead and the roof of the orbits, or eye sockets
- Supraorbital foramen (or notch)
- Forms a passageway above each orbit for blood vessels and nerves
- Frontal sinuses
- Air-filled cavities above the orbit
- Lined with mucous membrane
- Connect with the nasal cavity
- Reduce weight of the bone
43
The Parietal Bones
- Paired bones located posterior to frontal bone
- Form the roof and superior walls of the cranium
- Interlock along the midline of the cranium forming the sagittal suture
- Articulate with frontal bone along coronal suture
44
The Occipital Bone
-Forms the posterior and inferior portions of the cranium
-Articulates with two parietal bones at the lambdoid suture
-Foramen magnum
-Passageway surrounding the connection between the brain and the
spinal cord
-Occipital condyles
-Rounded surfaces on either side of the foramen magnum
-Articulate with the first vertebra
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The Temporal Bones
- Form part of both sides of the cranium and zygomatic arches
- Articulate with the parietal bones at the squamous suture
- House the auditory ossicles in middle ear
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Key bone markings
- External acoustic (or auditory) meatus
- Mandibular fossa
- Mastoid process
- Styloid process
47
The Sphenoid Bone
- Forms part of the floor of the cranium
- Acts as bridge, uniting cranial and facial bones
- Braces sides of skull
- Contains pair of sinuses (sphenoidal sinuses)
- “Wings” of the bone extend laterally from a central depression, the sella turcica
- Depression houses and protects the pituitary gland
48
The Ethmoid Bone
- Anterior to the sphenoid
- Forms part of the cranial floor
- Contributes to medial surfaces of the eye orbits and forms roof and sides of the nasal cavity
- Ridge called crista galli (“cock’s comb”) projects above superior surface
- Holes in cribriform plate allow olfactory nerves to pass through, carrying sense of smell
- Contains ethmoidal sinuses in lateral portions
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Superior and middle nasal conchae
- Project into nasal cavity toward nasal septum
| - Slows airflow, allowing time to clean, moisten, and warm air before entering respiratory tract
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Perpendicular plate
- Extends inferiorly from the crista galli between the conchae
- Forms part of the nasal septum
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Bones of the Face
- Protect and support entrances to digestive and respiratory tracts
- Sites for attachment of muscles for facial expression and manipulation of food
- Only one (the mandible) is movable
52
The Maxillary Bones
- Articulate with all other facial bones except for the mandible
- Largest facial bones
- Form the floor and medial parts of the orbit rims, the walls of the nasal cavity, and the anterior roof of the mouth (bony palate)
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Maxillary sinuses
- Produce mucus that drains into nasal cavities
| - Lighten the weight of the bones
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Infraorbital foramen
Opening for major sensory nerve from the face
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The Palatine Bones and Vomer
- Paired palatine bones form the posterior surface of the bony palate, or hard palate (the “roof” of the mouth)
- The L-shaped bones also contribute to the floor of the nasal cavity and floor of each orbit
- The vomer articulates with paired palatine bones
- Supports partition forming part of the nasal septum
56
The Zygomatic Bones
- Each zygomatic bone articulates with the frontal bone and the maxillae, forming the lateral wall of the orbit
- Temporal process of the zygomatic bone
- Curves laterally and posteriorly to articulate with the zygomatic process of the temporal bone
- Two processes together form the zygomatic arch, or cheekbone
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Nasal bones
- Form the bridge of the nose between the orbits
| - Articulate with the frontal and maxillary bones
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Lacrimal bones
- Located within the orbit on the medial surfaces
| - Articulate with the frontal, ethmoid, and maxillary bones
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Inferior nasal conchae
- Project from lateral walls of nasal cavity
- Change airflow and deflect air toward olfactory (smell) receptors
- Nasal Complex
- Nasal complex includes:
- All the bones that form the superior and lateral walls of nasal cavities
- Paranasal sinuses that drain into the nasal cavities
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Nasal septum
- Formed from ethmoid bone and vomer
| - Separates right and left portions of nasal cavity
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The Mandible
- Only bone of the lower jaw
- Vertical process (ramus) on either side extends toward the temporal bone and has two processes
- Posterior process is the condylar process
- Ends at mandibular condyle
- Articulates with the mandibular fossa of the temporal bone
- Anterior process is the coronoid process
- Attachment point for the temporalis muscle that closes the jaw
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The Hyoid Bone
-Small and U-shaped
-Suspended from the styloid processes of the temporal bones
Functions:
-Serves as base for muscles associated with the larynx (voicebox), tongue, and pharynx
-Supports and stabilizes the larynx
63
The Skulls of Infants and Children
- Skull formation begins with many different centers of ossification that fuse together
- Brain enlarges more rapidly than skull bones
- At birth cranial bones connected by areas of fibrous connective tissue known as fontanelles
- Anterior fontanelle commonly called the “soft spot”
- These flexible areas allow for easier delivery of the head
- Fontanelles disappear and skull growth is finished by about age four
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The Vertebral Column
- Also called the spine
- Consists of 26 bones
- 24 vertebrae
- The sacrum
- The coccyx, or tailbone
- Provides weight-bearing column of support and protection of spinal cord
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Cervical region
7 cervical vertebrae of the neck (C1 to C7)
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Thoracic region
- 12 thoracic vertebrae (T1 to T12)
| - Each vertebra articulates with one or more pairs of ribs
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Lumbar region
5 Lumbar vertebrae (L1 to L5)
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Sacral region
5 fused vertebrae form the single sacrum
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Coccygeal region
3–5 fused vertebrae form the coccyx
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Primary curves
- Are present at birth
| - Include the thoracic and sacral curves
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Secondary curves
- Develop several months after birth
- Include the cervical and lumbar curves
- All four spinal curves fully developed by age 10
- Three examples of abnormal spinal curvatures
- Kyphosis (exaggerated thoracic curvature)
- Lordosis (exaggerated lumbar curvature)
- Scoliosis (abnormal lateral curvature)
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Vertebral body
- More massive, weight-bearing portion of a vertebra
- Bodies of adjacent vertebrae separated from each other by intervertebral discs (except in sacrum and coccyx or between C1 and C2)
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Vertebral arch
- Forms posterior margin of vertebral foramen
- Vertebral foramina of successive vertebrae form the vertebral canal enclosing spinal cord
- Pedicles form walls of arch
- Roof of arch formed by laminae
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Transverse processes
- Project laterally or dorsolaterally from the pedicles
| - Sites for muscle attachment
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Spinous process, or spinal process
- Projects posteriorly from the laminae
| - Forms bumps that can be felt along midline of back
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Articular processes
- Arise at junction between pedicles and laminae on both sides of the vertebrae
- Each side of vertebra has superior and inferior articular process
- Processes of successive vertebrae contact one another at the articular facets
- Gaps between pedicles form the intervertebral foramina
- Allow passage of nerves to and from spinal cord
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The Cervical Vertebrae
- C1–C7
- Body is relatively small
- Distinctive features
- Oval, concave vertebral body
- Relatively large vertebral foramen
- Stumpy spinous process, usually with notched tip
- Round transverse foramina within transverse processes
- Protect blood vessels supplying brain
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The First Two Cervical Vertebrae (6-7)
- C1 is the atlas
- Holds up the head
- Articulates with the occipital condyles
- Allows for a specific “nodding yes” movement
- C2 is the axis
- Has a projection up toward the atlas, called the dens, or odontoid process
- Allows for rotational “shaking the head no” movement
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The Thoracic Vertebrae
- T1–T12
- Size of vertebral foramen decreases while size of body enlarges as progresses from T1–T12
- Distinctive features
- Heart-shaped body; larger than cervical vertebrae
- Large, slender spinous process that points inferiorly
- Costal facets that articulate with the ribs
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The Lumbar Vertebrae
- L1–L5
- The largest vertebrae with thickest intervertebral discs; support most of body weight
- Distinctive features
- Vertebral body is significantly thicker and more oval than thoracic vertebrae
- Massive, stumpy spinous process projecting posteriorly
- Bladelike transverse process lacking articulations for ribs
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The Sacrum
- Triangular-shaped bone
- Consists of five fused vertebrae
- Protects organs in pelvic cavity
- Has lateral articulations with pelvic girdle
- Broad surface provides attachment sites for muscles, especially those for leg movements
82
Features of the Sacrum
- Narrow caudal area is the apex
- Broad superior surface is the base
- Bulge at anterior tip of base is the sacral promontory
- Important landmark in females for labor and delivery
- Sacral canal extends along posterior surface
- Inferior end is the sacral hiatus
- Sacral foramina open on either side of median sacral crest
83
The Coccyx
- Three to five (usually four) fused vertebrae
- Fusion not complete until late in adulthood
- May fuse to sacrum in elderly people
- Provides attachment for muscles that close the anal opening
84
The Thoracic Cage
- Consists of thoracic vertebrae, the ribs, and the sternum
- Forms the walls of the thoracic cavity
- Protects heart, lungs, and internal organs
- Ribs and sternum form rib cage
- Ribs, or costal bones
- Long, curved, flattened bones
85
Ribs
- Ribs, or costal bones
- Twelve pairs
- First seven pairs are true ribs, or vertebrosternal ribs
- Connect to sternum by separate costal cartilages
- Ribs 8–12 are false ribs because do not attach directly to sternum
- Ribs 8–10 are vertebrochondral ribs whose costal cartilages fuse and merge together with cartilage 7
- Last two pairs (11 and 12) are floating ribs because have no connection with the sternum
86
The Sternum
- Also called the breastbone
- Consists of three parts that fuse by about age 25
1. Broad, triangular manubrium
- Articulates with the clavicles of the appendicular skeleton and cartilages of first pair of ribs
- Contains shallow indentation called jugular notch
2. Elongated body
3. Inferior tip, the xiphoid process
- Can be broken by impact or strong pressure such as with incorrect placement of hands during CPR
87
The Pectoral Girdle
- Also called the shoulder girdle
- Connects the upper limbs to the trunk
- Consists of the clavicle and the scapula
- Both bones are extremely important muscle attachment sites
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The Clavicle
- Clavicle
- S-shaped bone
- Articulates with manubrium at sternal end
- Articulates with the acromion of the scapula at the acromial end
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The Scapula
- Triangular bone
- Anterior surface of body of scapula bounded by superior, medial, and lateral borders
- The three tips are the superior, inferior, and lateral angles
- Lateral angle, or head of the scapula, contains the glenoid cavity, or glenoid fossa
- Articulates with the humerus to form the shoulder joint
90
Features of the Scapula
Subscapular fossa
-Depression in the anterior surface of the body where the subscapularis muscle attaches
Coracoid process
-Smaller, anterior projection over the glenoid cavity
Acromion
-Larger, posterior process that articulates with the distal end of the clavicle
Scapular spine
-Divides posterior surface of the scapula into the supraspinous fossa and the infraspinous fossa
91
The Upper Limb
Consists of the bones of the:
- Arm, or brachium
- The humerus
- Extends from the scapula to the elbow
- Forearm
- The radius and ulna
- Wrist and hand
- The carpals, metacarpals, and phalanges
92
The Humerus
- Rounded head at proximal end articulates with the scapula
- Greater tubercle is rounded projection on lateral surface of head
- Lesser tubercle lies anterior to and is separated from greater tubercle by the intertubercular groove
- Deltoid tuberosity runs along lateral border
- Attachment site for deltoid muscle
- Distally, the medial and lateral epicondyles project to either side
93
The Distal End of the Humerus
Smooth condyle articulates with radius and ulna
Medial trochlea extends from coronoid fossa to olecranon fossa
Fossae are depressions that articulate with projections from the ulna
Capitulum forms the lateral region of the condyle
Shallow radial fossa is proximal to the capitulum
Articulates with small projection from radius
94
The Radius and Ulna
-In anatomical position, radius lies along lateral side of forearm, while ulna is found on medial side
Ulna features
-Olecranon is the point of the elbow
-Trochlear notch articulates with the trochlea of the humerus
-Coronoid process forms the inferior lip of the notch
-Shaft ends distally at head of radius and short styloid process
-Interosseus membrane connects ulna and radius along length of bones
Radius features
-Radial head articulates with capitulum of humerus and radial notch of ulna, forming proximal radioulnar joint
-Neck of the radius is between the head and the radial tuberosity
-Distal styloid process of radius articulates with wrist (carpal bones)
95
The Bones of the Wrist
- Carpal bones of the wrist, or carpus
- Consists of eight bones arranged in two rows
- The proximal row includes:
- The scaphoid, lunate, triquetrum, and pisiform bones
- The distal row includes:
- The trapezium, trapezoid, capitate, and hamate bones
96
The Bones of the Hands
-Five metacarpal bones
-Form the palm of the hand
-Articulate with the phalanges or finger bones
-Each hand has 14 phalangeal bones
Proximal, middle, and distal in each finger
-Proximal and distal in the thumb, or pollex
97
The Pelvic Girdle
- Articulates with the thigh bones
- More massive than the pectoral girdle
- Firmly attached to the axial skeleton
- Consists of two large hip bones, or coxal bones
- Each a fusion of three bones: ilium, ischium, and pubis
- Hip bones articulate with the sacrum at the sacroiliac joints and with the femur at the acetabulum
98
The Hip Bone
- Ilium is superior and largest component
- Superior margin forms the iliac crest
- Ischium has a rough projection called ischial tuberosity
- Supports body’s weight when sitting
- Ischium branch fuses with the pubis, creating the circle of the obturator foramen
- Pubic bones articulate at the pubic symphysis
99
The Pelvis
- Consists of the hip bones, the sacrum, and the coccyx
- Stabilized by a network of ligaments
- Differences in male versus female pelvis
- Females: smoother, lighter in weight, less prominent markings
- Adaptations for childbearing: broad, low pelvis, larger pelvic outlet, broader pubic angle
100
The Lower Limb
Components include:
- Bones of the thigh
- The femur, or thigh bone
- The patella, or kneecap
- Bones of the leg
- The tibia and fibula
- Bones of the ankle and foot
- The tarsals, metatarsals, and phalanges
101
The Femur
- Longest and heaviest bone in the body
- Head articulates with pelvis at acetabulum
- Greater and lesser trochanters
- Large, rough projections extending laterally from neck and shaft
- Linea aspera
- Prominent ridge and attachment for adductor muscles
- Large epicondyles on distal end
- Inferior surfaces form lateral and medial condyles
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The Patella
- Patella, or kneecap
- Glides over smooth anterior surface, or patellar surface, between lateral and medial condyles of femur
- Forms within tendon of quadriceps femoris
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The Tibia
- Large, medial shinbone
- Lateral and medial condyles of tibia articulate with lateral and medial condyles of femur
- Patellar ligament connects patella to tibial tuberosity, rough spot just below knee joint
- Anterior margin extends down anterior tibial surface
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Medial malleolus
Large distal process that articulates with the ankle
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The Fibula
- Slender bone
- Runs parallel and lateral to tibia
- Articulates with tibia inferior to the lateral condyle of tibia
- Does not articulate with the femur
- Lateral malleolus is distal end of fibula
- Interosseus membrane connects tibia and fibula
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The Bones of the Ankle and Foot
- Seven ankle or tarsal bones include:
- Talus, calcaneus, navicular, and cuboid, and the medial, intermediate, and lateral cuneiforms
- Only the talus articulates with the tibia and fibula
- Largest tarsal is the calcaneus, or heel bone
- The metatarsals and phalanges are in the same pattern as in the hand
- Great toe is the hallux
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Arches of the Foot
- Longitudinal arch
- Transfers weight along the foot
- Maintained by ligaments and tendons
- Transverse arch
- Degree of curvature change from medial to lateral borders of the foot
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Categories of Joints, or Articulations
- Classified by structure
- Based on anatomy of joints
- Includes fibrous, cartilaginous (both with limited movement), and synovial (freely movable)
- Classified by function
- Based on range of motion
- Includes synarthrosis (immovable), amphiarthrosis (slightly movable), and diarthrosis (freely movable)
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Immovable Joints, or Synarthroses
-Can be fibrous or cartilaginous
Examples
-Suture
-Connects skull bones with dense connective tissue
-Gomphosis
-A ligament binding each tooth in the socket
-Synchondrosis
-A rigid cartilaginous connection as in between the first pair of ribs and the sternum
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Slightly Movable Joints, or Amphiarthroses
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-Can be fibrous or cartilaginous
Examples
-Syndesmosis
-Fibrous joint connected by a ligament
-Symphysis
-Cartilaginous joint between bones separated by fibrocartilage pad
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Freely Movable Joints, or Diarthroses
- Synovial joints with a wide range of motion
- Typically found at the ends of long bones
- Ends of bones covered with articular cartilages
- Joint surrounded with a fibrous joint capsule, or articular capsule
- Inner surfaces are lined with the synovial membrane
- Synovial fluid in the joint reduces friction
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Structure of a Synovial Joint
- Some synovial joints have additional padding
- For example, menisci in the knee
- Fat pads can also act as cushions
- Ligaments join bone to bone
- May be found inside and/or outside the joint capsule
- Bursae are packets of connective tissue containing synovial fluid
- Reduce friction and absorb shock
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Types of Synovial Joint Movement
- Gliding
- Two opposing surfaces slide past each other
- For example, between the carpal bones
- Angular movements include:
- Flexion, or decreasing the angle between articulating bones relative to anatomical position
- Example: moving the leg anteriorly at the hip
- Extension, or increasing the angle
- Hyperextension is extension beyond anatomical position
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Angular Movement
Abduction
-Moving a limb away from the longitudinal axis of the body or away from midline
Adduction
-Moving a limb toward the longitudinal axis of body or toward midline
Circumduction
-Moving the limbs in a loop
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Rotational Joint Movements
-Rotation involves turning around the longitudinal axis of the body or limb
-For example, turning the head, looking left to right
-Rotation of the distal end of the radius across the ulna is a form of rotation
Pronation
-Moving palm from palm-facing-front to palm-facing-back
Supination
-Opposite motion, turning to palm-facing-front
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Special Joint Movements
- Inversion twists the sole of the foot inward
- Eversion twists sole of foot outward
- Dorsiflexion elevates the sole at the ankle, as in digging in your heels
- Plantar flexion extends as in pointing the toes
- Opposition is moving the thumb toward the palm to grasp
- Reposition returns the thumb from opposition
- Elevation and depression
- Moving a structure superiorly and inferiorly
- For example, closing and opening your mouth
- Lateral flexion
- Bending of the vertebral column to the side
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Types of Synovial Joints
Gliding joints
-Have flat or slightly curved faces that slide across each other
-Movement is slight
Hinge joints
-Permit angular movement in one plane
-Like opening and closing a door
Condylar joints, or ellipsoidal joints
-Have an oval surface nestled within a depression on the opposing surface
Saddle joints
-Have two bones that each have a concave face on one axis and convex on the other
-Like a rider in a saddle
Pivot joints
-Permit rotation only
Ball-and-socket joints
-Occur where the end of one bone is a round head that nests within the cup-shaped depression in the other bone
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Intervertebral Articulations
- Two types of articulations between vertebrae
- Gliding joints between the superior and inferior articular processes
- Symphyseal joints between the vertebral bodies
- Separated and padded by intervertebral discs
- Discs made of a tough outer fibrocartilage layer surrounding a gelatinous core
- Discs compress with age, causing decrease in height
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The Shoulder Joint
- Permits the greatest range of motion of any joint
- Also most frequently dislocated
- Stability sacrificed for mobility
- Ball-and-socket joint
- Contains several large bursae to reduce friction
- Muscles that surround and move the shoulder joint form the rotator cuff
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The Elbow Joint
- Consists of two parts
- Hinge joint between the humerus and ulna
- Weak joint between the humerus and radius
- Hinge portion is very stable
- Humerus and ulna interlock
- Very thick joint capsule
- Joint capsule reinforced by strong ligaments
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The Hip Joint
- Ball-and-socket joint formed from head of the femur and the acetabulum
- Extremely stable joint
- Very dense and strong joint capsule
- Capsule reinforced by several ligaments
- Strong surrounding muscles
- Hip fractures more common than hip dislocations
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The Knee Joint
- Functions as hinge joint between femur and tibia
- Three separate articulations
- Two between femur and tibia where condyles contact
- One between patella and femur
- Medial and lateral menisci
- Fibrocartilage pads between femur and tibia
- Cushion and conform to changing shape with femoral movement
- Fat pads and bursae also assist in reducing friction
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Ligaments of the Knee Joint
- Patellar ligament
- Attaches to anterior surface of tibia
- Continuation of quadriceps tendon (which contains the patella)
- Provides support to front of the knee
- Posterior ligaments stabilize the back of the knee
- Fibular (lateral) and tibial (medial) collateral ligaments reinforce the sides of the knee
- Anterior and posterior cruciate ligaments located inside the joint capsule attach the tibia to femur
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Skeletal Support of Other Body Systems
- Balance between bone formation and recycling involves interactions with other systems
- Bones provide attachment sites for muscles
- Bones are extensively interconnected with cardiovascular and lymphatic systems
- Physiologically, bones are under the control of the endocrine system
- Digestive and urinary systems provide calcium and phosphate for bone growth
