Skeletal System

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Skeletal System

• Chapter 7
• Dr. Katherine Harris

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Bones are alive!

• Bone consists of a variety of active, LIVING
  tissues
• Bone tissue
• Cartilage
• Dense connective tissue
• Blood
• Nervous tissue

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Functions of Bone

• Organs of the skeletal system
• Provide points of attachment for muscles
• Protect support softer tissues
• House blood-producing cells
• Store inorganic salts
• Form passageways for blood vessels and nerves

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Bone and Muscle

• Both bone and muscle are living tissue
• separately neither is able to produce movement
• Muscular tissue contracts (gets shorter)
• when the muscle shortens, it pulls on the bone
• Bones are held together by joints, most of which
  permit movement between the bones
• pulling on one bone causes movement at the
  accompanying joint

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Body Movement

• Bones and Muscles interact as levers.

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Blood Cell Formation

• Hematopoiesis

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Bone Marrow

• The central canal of the long bone houses the
  marrow
• blood cells form in red marrow
• energy (fat) is stored in yellow marrow

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Bone Classification

• Bones are classified by their shapes
• Long bones
• Short bones
• Flat bones
• Irregular bones
• Sesamoid (round) bones

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Anatomy of a Typical Bone

• Dense compact bone surrounds the organ and spongy
  bone comprises the inner support
• The ends of the bones, or epiphyses, include the
  epiphyseal plate, an area of cartilage where long
  bones continue to grow during childhood and
  adolescence
• when bones cease growing, this cartilage is
  replaced by bone, leaving the epiphyseal line
• Wherever two bones meet, you will find a layer of
  hyaline cartilage
• this articulating cartilage prevents bone from
  grinding against bone at a joint

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Bone Tissue

• Two types of bone tissue
• Compact dense
• Spongy lighter and less dense than compact bone

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Compact Bone
Osteon concentric rings of matrix made by
osteocytes and formed surrounding a central canal.

• Compact bone material usually occurs at the edges
  of the bone and is composed of many individual
  osteons
• the central canal of the osteon houses the blood
  and nerve supply for the bone tissue

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Spongy Bone

• Spongy bone is less organized than compact bone
  and lacks osteons
• Instead, spongy bone has trabeculae, or struts,
  that form in response to stress

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Bone Development Growth

• The skeletal system begins to form during the
  first few weeks of prenatal development
• Bones continue to develop and grow into adulthood

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Bone Formation

• Bones are a form of connective tissue produced by
  immature bone cells called osteoblasts
• There are three types of cells that contribute to
  bone homeostasis.
• Osteoblasts are bone-forming cells
• Osteoclasts resorb or break down bone
• Osteocytes are mature bone cells
• An equilibrium between osteoblasts and
  osteoclasts maintains bone tissue.

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Bone Formation Ossification

• Ossification is the process of bone formation
• 2 types of ossification
• Most bones are endochondral (formed within
  cartilage)
• Intramembranous (cartilage is not involved)

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Bone Formation

• Intramembranous ossification forms the flat bones
  of the skull, clavicle, and mandible
• bone is laid down within embryonic connective
  tissue
• bones form deep in the dermis of the skin and
  thus are often called dermal bones

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Bone Formation

• Bones grow longer and thicker
• growth occurs at the outer surface of the bone
• cells within the membrane that covers the bone,
  the periosteum, differentiate into osteoblasts
  and begin to add matrix to the exterior
• accumulating matrix entraps these osteoblasts,
  which mature into osteocytes, creating new bone
  tissue around the exterior of the bone

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Bone Formation
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Bone Remodeling

• Bones are dynamic structures, constantly being
  remodeled and perfected to suit the needs of the
  body, and continuously making subtle changes in
  shape and density
• Bones cease growing in length at maturity, but
  continue to change shape throughout life

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Bone Remodeling Blood Calcium

• When the blood calcium level rises, the
  osteoblasts create new matrix, removing excess
  calcium from the blood.
• When the blood calcium level drops, osteoclasts
  go to work to release stored calcium to the
  blood.

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Osteoporosis

• Bone bank
• Calcium money
• The more you have in your account before age 30,
  the less likely you are to develop osteoporosis!

• Calcium rich foods
• Dairy products -- milk, cheese and yogurt
• Dark green leafy vegetables broccoli and
  spinach
• Calcium fortified foods -- orange juice, cereal
  and bread
• Nuts -- almonds

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Avoiding Osteoporosis

• Get at least 30 minutes of exercise daily
• A portion should be weight bearing exercise
• Consume enough daily calcium (1000-1200 mg)
• Consume enough daily vitamin D (200 IU)
• Avoid tobacco alcohol consumption

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The Skeleton

• The human skeleton is composed of 206 bones

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The Skeleton

• The skeleton is divided into
• the axial skeleton (the central axis of the body)
  
• the appendicular skeleton (the appendages and
  girdles holding them to the central axis)

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Cranial Bones

• Cranial bones surround and protect the brain
• the parietal and temporal bones are paired
• parietal bones protect the upper sides of the
  head
• temporal bones protect the middle sides of the
  head and support the ears
• the frontal bone, occipital bone, ethmoid, and
  sphenoid are single bones
• All 8 cranial bones are held together by fixed
  joints called sutures

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Facial Bones

• The 14 facial bones protect the entrances to the
  respiratory and digestive systems, and the
  sensory organs.
• Two facial bones are single, and 12 occur in
  pairs.

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Inferior View of Skull
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Sagittal Section of Skull
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Vertebrae

• These bones allow upright posture and protect
  vital organs of the thoracic cavity
• There are 24 vertebrae, one sacrum, and three to
  five coccyx bones in the adult vertebral column
• The sacrum is actually five fused vertebrae that
  form a solid base for the pelvic girdle
• The tailbone, or coccyx, is our post-anal tail

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Vertebrae

• A typical vertebra is composed of three parts
• the vertebral body
• the vertebral arch
• the vertebral articular processes
• serve as points of attachment between adjacent
  vertebra and sites for muscle attachment

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Vertebral Column

• The vertebral column is divided into 5 regions
• the cervical region
• the thoracic region
• the lumbar region
• the sacrum
• the coccyx
• Moving down the column, the bodies of the
  vertebrae grow larger, because they must support
  more weight

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Vertebral Column
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• Between each vertebra is a pad of fibrocartilage
  called the intervertebral disc
• the disc serves as a shock absorber, preventing
  vertebrae from rubbing against one another and
  crushing under the body's weight
• allows limited motion between vertebrae

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Vertebrae

• Vertebrae in different regions of the vertebral
  column have special characteristics.

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Sacrum Coccyx

• Sacrum
• Composed of 5 fused vertebrae
• Forms base of vertebral column
• Rows of openings provide passageways for nerves
  and blood vessels

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Sacrum Coccyx

• Coccyx (tailbone)
• Lowest part of vertebral column
• Composed of 4 fused vertebrae

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Ribs and Sternum

• 24 ribs, 1 pair attaches to each of the twelve
  thoracic vertebrae.
• 7 true ribs
• 5 false ribs
• 2 floating ribs
• The sternum, or breastbone, protects the anterior
  of the chest and has 3 parts
• Upper manubrium articulates with clavicle
• Middle body
• Lower xiphoid process

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The Appendicular Skeleton

• The appendicular skeleton includes all the bones
  that are attached, or appended, to the axial
  skeleton
• the pectoral girdle
• (shoulder bones)
• the upper appendages
• (arms and hands)
• the pelvic girdle
• (hips and pelvic bones)
• the lower appendages
• (legs and feet)

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The Pectoral Girdle and Upper Appendages

• Human bodies have two pectoral girdles
• each consisting of a clavicle and scapula
• The upper appendages
• the humerus is the longest and strongest bone in
  the upper appendicular skeleton
• the ulna and radius make up the forearm
• the elbow is the joint formed by the distal end
  of the humerus and the proximal ends of the
  radius and ulna
• The carpals (wrist bones) are in two rows of four
  short bones
• the metacarpals make up the structure of the hand
• the phalanges (finger bones) are considered long
  bones

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Pelvic Girdle

• The pelvic girdle
• composed of the hip bones and lower vertebrae
• denser, stronger, and less flexible than the
  appendicular girdle
• The acetabulum is the curved recess that serves
  as a socket for the head of the femur
• The pelvis is technically made of two large coxal
  bones (hip bones) which make up the pelvic
  girdle, plus the sacrum and the coccyx

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Right Hip Bone

• The hip bone emerges from three bones that fuse
  in early puberty
• the ilium
• the ischium
• the pubic bone
• the femur articulates at the junction of these
  three bones

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Right Lower Limb

• The femur is the longest and heaviest bone of the
  body. Makes up the upper leg.
• The fibula and tibia are found in the lower leg.
• The patella or knee cap is counted as a bone
• The tarsals, metatarsals and phalanges form the
  feet and toes.

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Joints

• Joints link the skeletal system together they
  exist wherever two bones meet
• Joints are classified by function or structure
• Functionally, joints are
• immovable or synarthrotic
• semimovable or amphiarthrotic
• freely movable or synovial (most common)
• Structurally, a joint is considered a fibrous,
  cartilaginous, or synovial joint

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Fibrous Joints

• Fibrous joints lie between bones that closely
  contact one another
• A thin layer of dense connective tissue joins the
  bones, as in a suture between a pair of flat
  bones of the skull

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Cartilaginous Joints

• Hyaline cartilage or fibrocartilage connect the
  bones of cartilaginous joints.
• This type of joint is found between the vertebrae
  of the vertebral column

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Synovial Joints

• Most common joint found within the skeletal
  system
• Allow free movement and are more structurally
  complex than fibrous or cartilaginous joints.
• Synovial fluid lubricates the joint.

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Lab This Week

• Intro to the skeletal system, skull vertebral
  column
• Bring your textbook and lab manual
• Well be covering Labs 12-14