The Skeletal System

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The Skeletal System
http//www.octc.kctcs.edu/gcaplan/anat/Notes/API
Notes H Skeletal System.htm
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Terminology

• 1Condyle Rounded prominence
• 2Facet Smooth articular surface
• 3Fissure Narrow opening
• 4Foramen Opening or hole through bone
• 5Fossa Depression or groove

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FISSURE
FISSURE
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FOSSA
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• 6Process Any bone projection
• 7Spine A narrow or pointed projection
• 8Trochanter A large, blunt process

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Notes H Skeletal Features.htm
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PROCESS
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SPINE
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TROCHANTER
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• 9).Tubercle A small, rounded process
• 10).Tuberosity A rounded, elevated area of a
  bone that is usually roughened

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Types of bones

• 4 types of bones.
• Long bones - longer than they are wide.
• Short bones - equal in length and width.
• Flat bones - thin and flat.
• Irregular bones do not fit into any of these
  categories.

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IRREGULAR BONES
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Bone Structure

• The shaft of the long bone is called the
  diaphysis.
• The extreme ends of the bones are known as the
  epiphyses.
• The diaphysis is between the two epiphyses.

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• Epiphysis of one bone meets the epiphysis of
  another bone is called a joint.
• Cartilage in joint known as the articular
  cartilage.

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• Bone - covered by a layer of connective tissue
  (periosteum).
• Provides nourishment attaches ligaments and
  tendons.

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• Two types of bone tissue in the diaphysis.
• Compact bone is tightly packed and forms the
  walls of the diaphysis.
• Spongy bone is less compact and is found in the
  diaphysis.

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• Within the spongy bone is red marrow.
• Within the diaphysis is a chamber called the
  medullary cavity.
• This cavity has yellow marrow which is used for
  energy storage.

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Leukemia

• Red marrow - makes red blood cells
  (hematopoiesis), white blood cells, and
  platelets.
• When white blood cells cant fight off infection,
  leukemia develops.
• Treatment for leukemia - injecting new bone
  marrow into the patient.

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Bone cells

• There are three types of bone cells.
• 1Osteoblasts - come from embryonic cells and
  found on surface of bone tissue.
• They lay bone down around themselves - become
  surrounded by bone matrix.
• Then they are called 2osteocytes.

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• 3Osteoclasts are found in the bone tissue and are
  involved with secretion of a substance that
  breaks down the bones.
• Osteoclasts help to break down the bone so that
  osteoblasts can lay new bone.
• This is how a bone grows.

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Under the microscope

• Osteocytes are found in spaces called lacunae,
  which are found between lamellae.
• These lamellae are layered in circles around
  canals known as Haversian canals.

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Bone Growth

• 2 forms of development.
• 1Intramembranous bones - cells develop between
  sheetlike layers of connective tissue.
• 2Endochondral bones - masses of cartilage are
  later replaced by bone tissue.

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• Intramembraneous bones - bones of the skull.
• Connective tissue appears where the bones will
  eventually be.
• Some of that connective tissue differentiates
  into the osteoblasts, which lay down bone.

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• In endochondral bone (most other bones) - masses
  of cartilage have same basic shape as future
  bones.
• The cartilage cells die - osteoblasts replace
  them.
• Happens in two stages - primary and secondary
  ossification centers.

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• When bone nears end of early development, a
  narrow band of cartilage remains between
  epiphyses and the diaphysis (epiphyseal plate)
• These are growth plates - located at each end of
  the bone.
• Determines how long your bones will be.

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• Growth plate injuries can happen.
• This is when the growth plate area is broken.
• In severe cases (only in children), it can stunt
  growth of the bone.
• When these growth plates close, you are done
  growing.

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• Osteoblasts and osteoclasts - lay down bone and
  breaking down bone.
• Once the epiphyseal plate is gone - done growing.
• The osteoblasts and osteoclasts are important in
  broken bones.

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Broken bones

• Complete fractures - bone is completely broken.
• Greenstick fracture - fracture is not completely
  through.
• Comminuted fracture - bone is shattered.

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Organization of Skeletal System

• Skeleton is divided into two parts.
• 1Axial skeleton - bones that are located
  medially.
• 2Appendicular skeleton - bones that are
  responsible for appendages.

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• Axial skeleton - skull, the hyoid bone, vertebral
  column, and thoracic cage.
• Appendicular skeleton - the pectoral girdle,
  upper limbs, pelvic girdle, and lower limbs.

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Axial Skeleton

• ASkull - Consists of 22 bones that are joined by
  sutures.
• Sutures are rigid, narrow joints.
• The soft spot in infants is an area where the
  sutures have not fully closed yet.

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• Sinuses - chambers in the skull that are lined
  with mucous membranes.
• Drain fluids, reduce the weight of the skull, and
  resonate sound from the voice.
• Sinuses can become infected (sinus infection).

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Bones of the skull

• The cranium encloses and protects the brain. It
  is made of 8 bones.
• 1Frontal bone large bone that forms the
  anterior part of the skull above the eyes.
  Contains the eye sockets (orbits).

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Frontal bone
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• Located above each orbit is the supraorbital
  foramen which is a hole through which blood
  vessels and nerves travel.
• The frontal bone also has the frontal sinuses.

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Supraorbital foramen
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• 2The parietal bones (2)
• Two parietal bones - one left and one right.
  Form the lateral part of the cranium.
• Meet at the top (the sagittal suture) meet the
  frontal bone at the coronal suture.

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Parietal bones
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• 3Occipital bone - forms the posterior wall of the
  cranium.
• Meets the parietal bones at the lambdoidal
  suture.
• Foramen magnum - large opening that allows spinal
  cord to pass between the cranium and the spinal
  cavity.

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Occipital Bone
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• 4Temporal bones (2) - on either side of the
  cranium (think temples!!)
• External auditory meatus located here and is the
  opening to the inner ear.
• Zygomatic arch (your cheekbone) joins the
  temporal bone to the zygomatic bone.

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Temporal Bone
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Zygomatic Arch
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• The mastoid process is located posterior and is
  the location of the attachment of neck muscles.
• The styloid process is the location of the
  attachment of the muscles of the tongue.

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Mastoid process
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Styloid process
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External auditory meatus
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• 5Sphenoid bone- wedged between other bones in the
  skull.
• Home of the optic foramen, where the optic nerve
  passes to go to the brain.
• Pituitary gland is housed in the sella turcica in
  the sphenoid bone.
• Sphenoidal sinuses here.

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Sphenoid Bone
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Sella Turcica (means Turkish saddle)
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Optic foramen
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• 6Ethmoid bone - anterior to the sphenoid.
• Mostly internal and forms part of nasal cavity.
• Ethmoid forms into the superior and middle nasal
  conchae (into the nostrils)
• Ethmoidal sinuses here.

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Nasal conchae
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• BFacial bones - 13 immovable bones in the face
  and a movable lower jaw.
• Support the face and provide attachments for the
  muscles that control facial expressions.

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• 1Maxillary bones - two bones located on side of
  the face that form the upper jaw.
• Maxillary sinuses (the largest ones) are located
  here.
• The roof of the mouth (including both palates)
  are formed by these bones.

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• 2Palatine bones - 2 L-shaped bones that are
  located posterior to the maxillary bones.
• Form the posterior roof of the mouth.

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• 3Zygomatic bones 2 bones that are found on the
  side of the face and form the cheekbones.
• Forms the zygomatic arch with the temporal bones.

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Zygomatic bones
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• 4Nasal bone - the two bones meet at the midline
  to form the bridge of the nose.
• The rest of the nose is formed from cartilage.

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Nasal Bones
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• 5Lacrimal bones 2 bones that are posterior and
  lateral to the nasal bones.
• Lacrimal means tears, so they are located in
  approximately the same area as your tear ducts.

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Lacrimal Bone
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• 6Vomer (1) - Located along the midline of the
  nasal cavity.
• The nasal septum divides the cavity into the left
  and right sides.
• A deviated septum is when the cavity is not
  divided into equal halves.

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Vomer
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• 7Inferior nasal conchae (2) - Found below the
  superior and middle conchae of the ethmoid bone.

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Inferior nasal conchae
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• 8Mandible - lower jaw bone that articulates with
  the temporal bones.
• The only movable bone of the skull.

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The hyoid bone

• This bone does not articulate with any other bone
  in the entire body.
• It supports the tongue and provides attachment
  for some of the muscles of the tongue.

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• CVertebral column - support for the trunk of the
  body.
• It runs from the skull to the pelvis.
• The bones that make up this column are known as
  vertebrae and are separated from each other by
  intervertebral discs.

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• A herniated disk happens when the disk breaks and
  puts pressure on the spinal nerve.

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• The 33 vertebrae are divided into regions.
• Cervical vertebrae (7) are in the neck.
• Thoracic vertebrae (12) in the thorax.

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• Lumbar vertebrae (5) in the lower trunk
• Sacral vertebrae (5) are fused (sacrum)
• The coccygeal (3-5) are fused (coccyx).
• Each region has a curve associated with it.

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• A vertebrae made up mostly of the body.
• Middle - vertebral foramen that the spinal cord
  passes through.
• Spiny part of the vertebrae called the spinous
  process.
• Connected to the body by pedicle.
• Transverse process are lateral projections.

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• The cervical vertebrae have two unique members.
• The atlas is the first vertebrae and it
  articulates with the skull.
• The second vertebrae is the axis and allows the
  nodding of the head by articulating with the
  atlas.

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• The thoracic vertebrae are larger than the
  cervical vertebrae.
• The lumbar vertebrae are thicker than the
  thoracic.
• The sacrum is triangular as a result of the
  fusion.
• The coccyx is your tailbone.

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• DThoracic cage - formed from the sternum and
  ribs.
• Sternum is the breastbone and located in the
  middle of the chest.
• It is made of three parts the superior
  manubrium, the body, and the inferior xiphoid
  process.

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• Ribs (12 pairs) attaches to individual thoracic
  vertebra sternum (by costal cartilage)
• First seven pairs of ribs are true ribs -
  attached at both points.
• Five pairs are false ribs have very little
  connection.
• Last two - floating ribs (no cartilage)

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Appendicular Skeleton

• AThe Pectoral Girdle - shoulder girdle is made up
  of two clavicles (collarbones) and two scapulae
  (shoulder blades)
• Scapulae have two processes (the coracoid process
  and the acromion process) allows for attachment
  of muscles.

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• BThe upper limb - humerus extends from scapula to
  elbow.
• The head of the humerus fits into the glenoid
  cavity of the scapula.
• The two tubercles (the greater and lesser)
  provide attachments for muscles.

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• Lower end of the humerous - two condyles that
  articulate with radius and ulna.
• Two fossas (the coronoid on the anterior side and
  the olecranon on the posterior side) allow for
  elbow movements.

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• Radius - bone located on thumb side of forearm
  extends from elbow to wrist.
• Head of radius articulates with humerus and a
  notch of the ulna.
• Radial tuberosity allows for muscle attachment
  and styloid process allows for wrist ligament
  attachment.

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Radius
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• Ulna is longer than radius and overlaps the end
  of the humerus.
• Proximal end - the ulna has a trochlear notch
  that articulates with the humerus.
• Two processes on either end of the notch the
  olecranon process and the coronoid process.

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• Distal end of ulna is the head that articulates
  with the radius.
• Ulna also has a styloid process that allows for
  attachment of the wrist ligaments.

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• Hand is composed of wrist, palm, and five
  fingers.
• Wrist is made up of eight carpal bones.
• The eight bones of the wrist are the lunate,
  hamate, triquetrum, pisiform, scaphoid, capitate,
  trapezoid, and trapezium.

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• Palm consists of five metacarpal bones.
• Finger bones are known as the phalanges.
• Each finger has proximal, middle, and distal
  phalanx (the thumb does not have the middle)

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• CPelvic girdle - 2 coxal bones that articulate
  with each other anteriorly and the sacrum
  posteriorly.
• Sacrum, coccyx, and pelvic girdle together form
  pelvis.
• Pelvis supports trunk of the body, provides
  attachments for lower limbs, and protects organs
  located in that area.

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• Coxal bone has three parts.
• Ilium is part of the bone that you think of as
  the hip. Flares outward and forms the bony
  prominence of the hip.
• Top of this is called the iliac crest.
• Ilium joins the sacrum at the sacroiliac joint
  and has anterior superior iliac spine which
  provides attachments for muscles.

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• Ischium forms the lowest portion of the coxal
  bone.
• Ischial tuberosity points posteriorly and
  downward and provides attachment for muscles and
  ligaments.
• Where the ilium meets the ischium is a projection
  called the ischial spine.

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• Pubis is anterior part of the coxal bone.
• 2 pubic bones join at midline, forming a joint
  called the symphysis pubis.
• Angle of these bones below the symphysis pubis is
  called pubic arch.
• Obturator foramen is found in pelvic girdle and
  is the largest in the body.

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• DLower limbs form thigh, leg, and foot.
• Femur is longest bone in the body and extends
  from hip to the knee.
• Head of the femur fits in the acetabulum of the
  coxal bone.
• On head is fovea capitis which allows attachment
  of a ligament.

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• Below the head 2 processes the greater
  trochanter and the lesser trochanter.
• Distal end of femur - 2 condyles (lateral and
  medial) that articulate with tibia of the leg.
• Patella (kneecap) articulates with femur at
  distal end.

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• Tibia shinbone larger of two lower leg bones
  (located medially).
• Proximal end has medial and lateral condyles that
  articulate with the condyles of the femur.
• Below condyles is tibial tuberosity.
• Distal end - medial malleolus.

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• Fibula - smaller lower leg bone.
• Has a head at the proximal end and a lateral
  malleolus at the distal end.
• The lateral malleolus is responsible for the bump
  you feel on the side of your ankle.

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• Foot - 7 tarsal bones (calcaneous, talus,
  navicular, cuboid, lateral cuneiform,
  intermediate cuneiform, and the medial cuneiform)
• Talus moves freely where it meets the fibula and
  tibia.
• Calcaneous - largest (heel bone)

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Talus
Calcaneus
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• Tarsal bones articulate with metatarsals.
• 5 metatarsals articulate with phalanges (the
  toes).
• 3 phalanges for each toe the proximal, middle,
  and distal phalange.
• Big toe does not have a middle one.

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• http//www.cdc.gov/powerfulbones/images/skeleton2.
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Diseases

• 1Achondroplasia form of dwarfism.
• Due to cartilage converting to bone during
  development.
• Normal-size trunk and head short extremities.

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• 2Osteoporosis occurs when the rate of bone
  formation and bone resorption changes.
• Results in fragile bones that break easily.

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• 3Rheumatoid Arthritis cartilage and dense
  connective tissue breakdown easily.
• The joint eventually fuses with the bone.
• Autoimmune disease persons immune system
  attacks itself.

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