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Skeletal System

Lecture A

The Skeletal System

  • parts of the skeletal system

    • bones (skeleton)

    • joints

    • cartilages

    • ligaments

  • two subdivisions of the skeleton

    • axial skeleton

    • appendicular skeleton

Function of Bones

  • support the body

  • protect soft organs

  • allow movement due to attached skeletal muscles

  • store minerals and fats

  • blood cell formation

Bones of the Human Body

  • the adult skeleton has 206 bones

  • two basic types of bone tissue

    • compact bone

      • homogeneous

    • spongy bone

      • small needle-like pieces of bone

      • many open spaces

Classification of Bones

  • Long Bones

    • typically larger than they are wide

    • have a shaft with heads at both ends

    • contain mostly compact bone

    • examples

      • femur

      • humerus

  • Short Bones

    • generally cube-shaped

    • contain mostly spongy bone

    • examples

      • carpals

      • tarsals

  • Flat Bones

    • thin, flattened, and usually curved

    • two thin layers of compact bone surround a layer of spongy bone

    • examples

      • skull

      • ribs

      • sternum

  • Irregular Bones

    • irregular shape

    • do not fit into other bone classification categories

    • examples

      • vertebrae

      • hip bones

Anatomy of a Long Bone

  • Diaphysis

    • shaft

    • composed of compact bone

  • Epiphysis

    • ends of the bone

    • composed of mostly spongy tissue

  • Periosteum

    • the outside covering of the diaphysis

    • fibrous connective tissue membrane

  • Sharpey’s Fibers

    • secure periosteum to underlying bone

  • Arteries

    • supply bone cells with nutrients

  • Articular Cartilage

    • covers the external surface of the epiphysis

    • made of hyaline cartilage

    • decreases friction at joint surfaces

  • Epiphyseal Plate

    • flat plate of hyaline cartilage seen in young, growing bones

  • Epiphyseal Line

    • remnant of the epiphyseal plate

    • seen in adult bones

  • Medullary Cavity

    • cavity inside of the shaft

    • contains yellow marrow (mostly fat) in adults

    • contains red marrow (for blood cell formations) in infants

Bone Markings

  • surface features of bones

    • sites of attachments for muscles, tendons, and ligaments

    • passages for nerves and blood vessels

  • categories of bone markings

    • projections or processes - grow out from the bone surface

    • depressions or cavities - indentations

Microscopic Anatomy of Bone

  • Osteon (Haversian System)

    • a unit of bone containing a central canal and matrix ring

  • Central (Haversian) Canal

    • opening in the center of an osteon

    • carries blood vessels and nerves

  • Perforating (Volkman’s) Canal

    • canal perpendicular to the central canal

    • carries blood vessels and nerves

  • Lacunae

    • cavities containing bone cells (osteocytes)

    • arranged in concentric rings

  • Lamellae

    • rings around the central canal

    • sites of lacunae

  • Canaliculi

    • tiny canals

    • radiate from central canal to lacunae

    • form a transport system connecting all bone cells to a nutrient supply

Formation of the Human Skeleton

  • in embryos, the skeleton is primarily hyaline cartilage

  • during development, much of this cartilage is replaced by bone

  • cartilage remains in isolated areas

    • bridge of the nose

    • parts of ribs

    • joints

Bone Growth (Ossification)

  • epiphyseal plate allows for lengthwise growth of long bones during childhood

    • new cartilage is continuously ossified

    • enclosed cartilage is digested away, opening up a medullary cavity

    • bone replaces cartilage through the action of osteoblasts

  • bones are remodeled and lengthened until growth stops

    • bones are remodeled in response to two factors

      • blood calcium levels

      • pull of gravity and muscles of the skeleton

    • bones grow in width (called appositional growth)

Types of Bone Cells

  • osteocytes

    • mature bone cells

  • osteoblasts

    • bone-forming cells

  • osteoclasts

    • bone-destroying cells

  • bone remodeling

    • performed by both osteoblasts and osteoclasts

Lecture B

Bone Fractures

  • fracture - break in a bone

  • types of bone fractures

    • closed (simple) fracture - break does not penetrate the skin

    • open (compound) fracture - broken bone penetrates the skin

  • bone fractures are treated by reduction and immobilization

Repair of Bone Fractures

  • hematoma (blood-filled swelling) is formed

  • break is splinted by fibrocartilage to form a callus

  • fibrocartilage callus is replaced by bony callus

  • bony callus is remodeled to form a permanent patch

The Axial Skeleton

  • forms the longitudinal axis of the body

  • divided into three parts

    • skull - cranium and facial bones

    • vertebral column - cervical, thoracic, lumbar, and sacrum regions

    • bony thorax - ribcage and sternum

The Skull

  • two sets of bones

    • cranium

    • facial bones

  • bones are joined by sutures

  • only the mandible is attached by a freely movable joint

Paranasal Sinuses

  • hollow portions of bones surrounding the nasal cavity

  • functions of paranasal sinuses

    • lighten the skull

    • give resonance and amplification

The Hyoid Bone

  • the only bone that does not articulate with another bone

  • serves as a moveable base for the tongue

  • aids in swallowing and speech

Lecture C

The Fetal Skull

  • large compared to the infant’s total body length

  • Fontanels - fibrous membranes connecting the cranial bones

    • allow the brain to grow

    • convert to bone within 24 months after birth

The Vertebral Column

  • each vertebrae is given a name according to its location

    • there are 24 single vertebral bones separated by intervertebral discs

      • seven cervical vertebrae

        • C1 - atlas

        • C2 - axis

      • twelve thoracic vertebrae

      • five lumbar vertebrae

    • nine vertebrae form two composite bones

      • sacrum

      • coccyx

  • the spine has a normal curvature

    • primary curvatures are the spinal curvatures of the thoracic and sacral regions

      • present from birth

    • secondary curvatures are the spinal curvatures of the cervical and lumbar regions

      • present after birth

    • Irregular curvatures

      • Scoliosis - left or right curvature

      • Kyphosis - hump at the top (dowagers hump)

      • Lordosis - inward curvature of the lumbar region

Sacrum and Coccyx

  • Sacrum

    • formed by the fusion of five vertebrae

  • Coccyx

    • formed from the fusion of three to five vertebrae

    • “tailbone” or remnant of a tail that other vertebrae have

The Bony Thorax

  • forms a cage to protect major organs

  • consists of three parts

    • sternum

      • manubrium - the top part

    • ribs

      • true ribs (pairs 1-7)

      • false ribs (pairs 8-12)

      • floating ribs (pairs 11-12)

    • thoracic vertebrae

Lecture D

The Appendicular Skeleton

  • composed of 126 bones

    • limbs (appendages)

    • pectoral girdle

    • pelvic girdle

The Pectoral (Shoulder) Girdle

  • composed of two bones

    • clavicle - collarbone

    • scapula - shoulder blade

  • these bones allow the upper limb to have exceptionally free movement

Bones of the Upper Limbs

  • humerus

    • forms the arm

    • single bone

  • the forearm has two bones

    • ulna

      • the medial bone in anatomical position

    • radius

      • lateral bone in anatomical position

  • the hand

    • carpals - wrist

    • metacarpals - palm

    • phalanges - fingers

Lecture E

Bones of the Pelvic Girdle

  • formed by two coxal (ossa coxae) bones

  • composed of three pairs of fused bones

    • ilium

    • ischium

    • pubis

  • the total weight of the upper body rests on the pelvis

  • it protects several organs

    • reproductive organs

    • urinary bladder

    • part of the large intestine

Gender Differences of the Pelvis

  • the female inlet is larger and more circular

  • the female pelvis as a whole is shallower, and the bones are lighter and thinner

  • the female ilia flare more laterally

  • the female sacrum is shorter and less curved

  • the female ischial spines are shorter and farther apart; thus the outlet is larger

  • the female pubic arch is more rounded because the angle of the pubic arch is greater

Bones of the Lower Limbs

  • the thigh has one bone

    • femur

      • the heaviest, strongest bone in the body

  • the lower leg has two bones

    • tibia

      • shinbone

      • larger and medially oriented

    • fibula

      • thin and sticklike

  • the foot

    • tarsals

      • two largest tarsals

        • calcaneus (heel bone)

        • talus

    • metatarsals - sole

    • phalanges - toes

Arches of the Foot

  • bones of the foot are arranged to form three strong arches

    • two longitudinal

    • one transverse

Lecture F

Joints

  • articulations of bones

  • functions of joints

    • hold bones together

    • allow for mobility

  • ways joints are classified

    • functionally

    • structurally

Functional Classification of Joints

  • synarthroses

    • immovable joints

  • amphiarthroses

    • slightly moveable joints

  • diarthrosis

    • freely moveable joints

Structural Classification of Joint

  • fibrous joints

    • generally immovable

  • cartilaginous joints

    • immovable or slightly moveable

  • synovial joints

    • freely moveable

Fibrous Joints

  • bones united by fibrous tissue

  • example

    • sutures

    • syndesmoses

      • allows more movement than sutures

      • example: the distal end of the tibia and fibula

Cartilaginous Joints

  • bones connected by cartilage

  • example

    • pubic symphysis

    • intervertebral joints

Synovial Joints

  • articulating bones are separated by a joint cavity

  • synovial fluid is found in the joint cavity

  • types of synovial joints

    • plane joint

    • hinge joint

    • pivot joint

    • condyloid joint

    • saddle joint

    • ball and socket joint

Features of Synovial Joints

  • articular cartilage (hyaline cartilage) covers the ends of bones

  • a fibrous articular capsule encloses joint surfaces

  • a joint cavity is filled with synovial fluid

  • ligaments reinforce the joint

Structures Associated with the Synovial Joint

  • bursae - flattened fibrous sacs

    • lined with synovial membranes

    • filled with synovial fluid

    • not actually part of the joint

  • tendon sheath

    • elongated bursa that wraps around a tendon

Inflammatory Conditions Associated with Joints

  • bursitis - inflammation of a bursa usually caused by a blow or friction

  • tendonitis - inflammation of tendon sheaths

  • arthritis - inflammatory or degenerative diseases of joints

    • over 100 different types

    • the most widespread crippling disease in the United States

Clinical Forms of Arthritis

  • osteoarthritis

    • the most common chronic arthritis

    • probably related to normal aging processes

  • rheumatoid arthritis

    • an autoimmune disease - the immune system attacks the joints

    • symptoms begin with bilateral inflammation of certain joints

    • often leads to deformities

  • Gouty arthritis

    • inflammation of joints is caused by a deposition of uric acid crystals from the blood

    • can usually be controlled with diet

    • high protein diet can contribute to the production of uric acid crystals

Developmental Aspects of the Skeletal System

  • at birth, the skull bones are incomplete

  • bones are joined by fibrous membranes called fontanels

  • fontanels are completely replaced with bone within two years after birth

Skeletal Changes Throughout Life

  • fetus

    • long bones are formed of hyaline cartilage

    • flat bones begin as fibrous membranes

    • flat and long bone models are converted to bone

  • birth

    • fontanels remain until around age 2

  • adolescence

    • epiphyseal plates become ossified and long bone growth ends

  • size of the cranium in relationship to the body

    • 2 years old - the skull is larger in proportion to the body compared to that of an adult

    • 8 or 9 years old - the skull is near the adult size and proportion

    • between ages 6 and 11, the face grows out from the skull

  • curvatures of the spine

    • primary curvatures are present at birth and are convex posteriorly

    • secondary curvatures are associated with a child’s later development and are convex anteriorly

    • abnormal spinal curvatures (scoliosis and lordosis) are often congenital

  • osteoporosis (homeostatic imbalance)

    • bone-thinning disease afflicting

      • 50% of women over age 65

      • 20% of men over age 70

    • disease makes bones fragile and bones can easily fracture

    • vertebral collapse results in kyphosis

      • aka dowagers hump

    • estrogen aids in the health and normal density of a female skeleton

Skeletal System

Lecture A

The Skeletal System

  • parts of the skeletal system

    • bones (skeleton)

    • joints

    • cartilages

    • ligaments

  • two subdivisions of the skeleton

    • axial skeleton

    • appendicular skeleton

Function of Bones

  • support the body

  • protect soft organs

  • allow movement due to attached skeletal muscles

  • store minerals and fats

  • blood cell formation

Bones of the Human Body

  • the adult skeleton has 206 bones

  • two basic types of bone tissue

    • compact bone

      • homogeneous

    • spongy bone

      • small needle-like pieces of bone

      • many open spaces

Classification of Bones

  • Long Bones

    • typically larger than they are wide

    • have a shaft with heads at both ends

    • contain mostly compact bone

    • examples

      • femur

      • humerus

  • Short Bones

    • generally cube-shaped

    • contain mostly spongy bone

    • examples

      • carpals

      • tarsals

  • Flat Bones

    • thin, flattened, and usually curved

    • two thin layers of compact bone surround a layer of spongy bone

    • examples

      • skull

      • ribs

      • sternum

  • Irregular Bones

    • irregular shape

    • do not fit into other bone classification categories

    • examples

      • vertebrae

      • hip bones

Anatomy of a Long Bone

  • Diaphysis

    • shaft

    • composed of compact bone

  • Epiphysis

    • ends of the bone

    • composed of mostly spongy tissue

  • Periosteum

    • the outside covering of the diaphysis

    • fibrous connective tissue membrane

  • Sharpey’s Fibers

    • secure periosteum to underlying bone

  • Arteries

    • supply bone cells with nutrients

  • Articular Cartilage

    • covers the external surface of the epiphysis

    • made of hyaline cartilage

    • decreases friction at joint surfaces

  • Epiphyseal Plate

    • flat plate of hyaline cartilage seen in young, growing bones

  • Epiphyseal Line

    • remnant of the epiphyseal plate

    • seen in adult bones

  • Medullary Cavity

    • cavity inside of the shaft

    • contains yellow marrow (mostly fat) in adults

    • contains red marrow (for blood cell formations) in infants

Bone Markings

  • surface features of bones

    • sites of attachments for muscles, tendons, and ligaments

    • passages for nerves and blood vessels

  • categories of bone markings

    • projections or processes - grow out from the bone surface

    • depressions or cavities - indentations

Microscopic Anatomy of Bone

  • Osteon (Haversian System)

    • a unit of bone containing a central canal and matrix ring

  • Central (Haversian) Canal

    • opening in the center of an osteon

    • carries blood vessels and nerves

  • Perforating (Volkman’s) Canal

    • canal perpendicular to the central canal

    • carries blood vessels and nerves

  • Lacunae

    • cavities containing bone cells (osteocytes)

    • arranged in concentric rings

  • Lamellae

    • rings around the central canal

    • sites of lacunae

  • Canaliculi

    • tiny canals

    • radiate from central canal to lacunae

    • form a transport system connecting all bone cells to a nutrient supply

Formation of the Human Skeleton

  • in embryos, the skeleton is primarily hyaline cartilage

  • during development, much of this cartilage is replaced by bone

  • cartilage remains in isolated areas

    • bridge of the nose

    • parts of ribs

    • joints

Bone Growth (Ossification)

  • epiphyseal plate allows for lengthwise growth of long bones during childhood

    • new cartilage is continuously ossified

    • enclosed cartilage is digested away, opening up a medullary cavity

    • bone replaces cartilage through the action of osteoblasts

  • bones are remodeled and lengthened until growth stops

    • bones are remodeled in response to two factors

      • blood calcium levels

      • pull of gravity and muscles of the skeleton

    • bones grow in width (called appositional growth)

Types of Bone Cells

  • osteocytes

    • mature bone cells

  • osteoblasts

    • bone-forming cells

  • osteoclasts

    • bone-destroying cells

  • bone remodeling

    • performed by both osteoblasts and osteoclasts

Lecture B

Bone Fractures

  • fracture - break in a bone

  • types of bone fractures

    • closed (simple) fracture - break does not penetrate the skin

    • open (compound) fracture - broken bone penetrates the skin

  • bone fractures are treated by reduction and immobilization

Repair of Bone Fractures

  • hematoma (blood-filled swelling) is formed

  • break is splinted by fibrocartilage to form a callus

  • fibrocartilage callus is replaced by bony callus

  • bony callus is remodeled to form a permanent patch

The Axial Skeleton

  • forms the longitudinal axis of the body

  • divided into three parts

    • skull - cranium and facial bones

    • vertebral column - cervical, thoracic, lumbar, and sacrum regions

    • bony thorax - ribcage and sternum

The Skull

  • two sets of bones

    • cranium

    • facial bones

  • bones are joined by sutures

  • only the mandible is attached by a freely movable joint

Paranasal Sinuses

  • hollow portions of bones surrounding the nasal cavity

  • functions of paranasal sinuses

    • lighten the skull

    • give resonance and amplification

The Hyoid Bone

  • the only bone that does not articulate with another bone

  • serves as a moveable base for the tongue

  • aids in swallowing and speech

Lecture C

The Fetal Skull

  • large compared to the infant’s total body length

  • Fontanels - fibrous membranes connecting the cranial bones

    • allow the brain to grow

    • convert to bone within 24 months after birth

The Vertebral Column

  • each vertebrae is given a name according to its location

    • there are 24 single vertebral bones separated by intervertebral discs

      • seven cervical vertebrae

        • C1 - atlas

        • C2 - axis

      • twelve thoracic vertebrae

      • five lumbar vertebrae

    • nine vertebrae form two composite bones

      • sacrum

      • coccyx

  • the spine has a normal curvature

    • primary curvatures are the spinal curvatures of the thoracic and sacral regions

      • present from birth

    • secondary curvatures are the spinal curvatures of the cervical and lumbar regions

      • present after birth

    • Irregular curvatures

      • Scoliosis - left or right curvature

      • Kyphosis - hump at the top (dowagers hump)

      • Lordosis - inward curvature of the lumbar region

Sacrum and Coccyx

  • Sacrum

    • formed by the fusion of five vertebrae

  • Coccyx

    • formed from the fusion of three to five vertebrae

    • “tailbone” or remnant of a tail that other vertebrae have

The Bony Thorax

  • forms a cage to protect major organs

  • consists of three parts

    • sternum

      • manubrium - the top part

    • ribs

      • true ribs (pairs 1-7)

      • false ribs (pairs 8-12)

      • floating ribs (pairs 11-12)

    • thoracic vertebrae

Lecture D

The Appendicular Skeleton

  • composed of 126 bones

    • limbs (appendages)

    • pectoral girdle

    • pelvic girdle

The Pectoral (Shoulder) Girdle

  • composed of two bones

    • clavicle - collarbone

    • scapula - shoulder blade

  • these bones allow the upper limb to have exceptionally free movement

Bones of the Upper Limbs

  • humerus

    • forms the arm

    • single bone

  • the forearm has two bones

    • ulna

      • the medial bone in anatomical position

    • radius

      • lateral bone in anatomical position

  • the hand

    • carpals - wrist

    • metacarpals - palm

    • phalanges - fingers

Lecture E

Bones of the Pelvic Girdle

  • formed by two coxal (ossa coxae) bones

  • composed of three pairs of fused bones

    • ilium

    • ischium

    • pubis

  • the total weight of the upper body rests on the pelvis

  • it protects several organs

    • reproductive organs

    • urinary bladder

    • part of the large intestine

Gender Differences of the Pelvis

  • the female inlet is larger and more circular

  • the female pelvis as a whole is shallower, and the bones are lighter and thinner

  • the female ilia flare more laterally

  • the female sacrum is shorter and less curved

  • the female ischial spines are shorter and farther apart; thus the outlet is larger

  • the female pubic arch is more rounded because the angle of the pubic arch is greater

Bones of the Lower Limbs

  • the thigh has one bone

    • femur

      • the heaviest, strongest bone in the body

  • the lower leg has two bones

    • tibia

      • shinbone

      • larger and medially oriented

    • fibula

      • thin and sticklike

  • the foot

    • tarsals

      • two largest tarsals

        • calcaneus (heel bone)

        • talus

    • metatarsals - sole

    • phalanges - toes

Arches of the Foot

  • bones of the foot are arranged to form three strong arches

    • two longitudinal

    • one transverse

Lecture F

Joints

  • articulations of bones

  • functions of joints

    • hold bones together

    • allow for mobility

  • ways joints are classified

    • functionally

    • structurally

Functional Classification of Joints

  • synarthroses

    • immovable joints

  • amphiarthroses

    • slightly moveable joints

  • diarthrosis

    • freely moveable joints

Structural Classification of Joint

  • fibrous joints

    • generally immovable

  • cartilaginous joints

    • immovable or slightly moveable

  • synovial joints

    • freely moveable

Fibrous Joints

  • bones united by fibrous tissue

  • example

    • sutures

    • syndesmoses

      • allows more movement than sutures

      • example: the distal end of the tibia and fibula

Cartilaginous Joints

  • bones connected by cartilage

  • example

    • pubic symphysis

    • intervertebral joints

Synovial Joints

  • articulating bones are separated by a joint cavity

  • synovial fluid is found in the joint cavity

  • types of synovial joints

    • plane joint

    • hinge joint

    • pivot joint

    • condyloid joint

    • saddle joint

    • ball and socket joint

Features of Synovial Joints

  • articular cartilage (hyaline cartilage) covers the ends of bones

  • a fibrous articular capsule encloses joint surfaces

  • a joint cavity is filled with synovial fluid

  • ligaments reinforce the joint

Structures Associated with the Synovial Joint

  • bursae - flattened fibrous sacs

    • lined with synovial membranes

    • filled with synovial fluid

    • not actually part of the joint

  • tendon sheath

    • elongated bursa that wraps around a tendon

Inflammatory Conditions Associated with Joints

  • bursitis - inflammation of a bursa usually caused by a blow or friction

  • tendonitis - inflammation of tendon sheaths

  • arthritis - inflammatory or degenerative diseases of joints

    • over 100 different types

    • the most widespread crippling disease in the United States

Clinical Forms of Arthritis

  • osteoarthritis

    • the most common chronic arthritis

    • probably related to normal aging processes

  • rheumatoid arthritis

    • an autoimmune disease - the immune system attacks the joints

    • symptoms begin with bilateral inflammation of certain joints

    • often leads to deformities

  • Gouty arthritis

    • inflammation of joints is caused by a deposition of uric acid crystals from the blood

    • can usually be controlled with diet

    • high protein diet can contribute to the production of uric acid crystals

Developmental Aspects of the Skeletal System

  • at birth, the skull bones are incomplete

  • bones are joined by fibrous membranes called fontanels

  • fontanels are completely replaced with bone within two years after birth

Skeletal Changes Throughout Life

  • fetus

    • long bones are formed of hyaline cartilage

    • flat bones begin as fibrous membranes

    • flat and long bone models are converted to bone

  • birth

    • fontanels remain until around age 2

  • adolescence

    • epiphyseal plates become ossified and long bone growth ends

  • size of the cranium in relationship to the body

    • 2 years old - the skull is larger in proportion to the body compared to that of an adult

    • 8 or 9 years old - the skull is near the adult size and proportion

    • between ages 6 and 11, the face grows out from the skull

  • curvatures of the spine

    • primary curvatures are present at birth and are convex posteriorly

    • secondary curvatures are associated with a child’s later development and are convex anteriorly

    • abnormal spinal curvatures (scoliosis and lordosis) are often congenital

  • osteoporosis (homeostatic imbalance)

    • bone-thinning disease afflicting

      • 50% of women over age 65

      • 20% of men over age 70

    • disease makes bones fragile and bones can easily fracture

    • vertebral collapse results in kyphosis

      • aka dowagers hump

    • estrogen aids in the health and normal density of a female skeleton

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