Anatomy and Physiology

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Anatomy and Physiology

• Skeletal System
• part II

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Skeletal Organization

• The skeleton can be divided into
• Axial portion (head, neck, and trunk)
• Appendicular portion (arms and legs).

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• The axial skeleton consists of
• The skull
• Hyoid bone
• Vertebral column
• Thoracic cage.

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• The appendicular skeleton consists of
• Pectoral girdle
• Upper limbs
• Pelvic girdle
• Lower limbs

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• 206 bones in an adult skeleton

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Skull

• The skull consists of twenty-two bones.
• 8 cranial bones
• 14 facial bones
• 1 mandible

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Skull

• Cranium (braincase)
• The cranium encloses and protects the brain
• Surface of the cranium provides attachments for
  muscles used in chewing and head movements

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• Some cranial bones contain air-filled paranasal
  sinuses.
• Sinuses are lined with mucous membranes and are
  connected to the nasal cavity
• Sinuses reduce the skulls weight and increase
  voice intensity by resonance

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• Cranial bones include

• Frontal bone
• Parietal bones
• Occipital bone
• Temporal bone
• Sphenoid bone
• Ethmoid bone

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• Sutures immovable joint along which flat bones
  of the cranium are joined

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Facial Skeleton

• Facial bones
• Form the basic shape of the face
• Provide attachments for muscles that move the jaw
• Control facial expressions

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Facial Skeleton

• Facial bones include

• Maxillae
• Palatine bones
• Zygomatic bones
• Lacrimal bones
• Nasal bones
• Vomer bone
• Inferior nasal conchae
• Mandible

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Mandible

• The lower jawbone
• The only movable bone of the skull
• Held to the cranium by ligaments

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Cleft Palate

• Incomplete fusion of the palatine processes of
  the maxillae
• Causes problems with sucking, eating, and
  speaking
• Corrective surgery is needed to close the opening
  between the oral and nasal cavities

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Infantile Skull

• Proportions of the infantile skull are different
  from those of an adult skull.
• Small face with prominent forehead and large
  orbits
• Smaller jaw and nasal cavity
• Frontal bone in two parts

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Infantile Skull

• Fontanels (fibrous membranes) connect
  incompletely developed bones
• Called soft spots
• Permit movement between bones so that developing
  skull can change shape as it moves through the
  birth canal
• Eventually close as cranial bones grow together

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Hyoid Bone

• Located in the neck between the lower jaw and the
  larynx
• Supports tongue and attachment site for muscles
  used during swallowing

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Vertebral Column

• Backbone or Spine
• The vertebral column extends from the skull to
  the pelvis

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Vertebral Column

• Protects the spinal cord which passes through the
  vertebral canal
• Supports the head and trunk

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Vertebral Column (backbone)

• It is composed of vertebrae, separated by
  intervertebral disks and are connected to one
  another by ligaments

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A Typical Vertebra

• A typical vertebra consists of
• Body forms the thick anterior portion
• Bony vertebral arch surrounds the spinal cord.
• Notches on the upper and lower surfaces provide
  intervertebral foramina (openings) through which
  spinal nerves pass.

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Spina Bifida

• Occurs if the laminae of the vertebral arch fail
  to unite during development.
• Contents of the vertebral canal protrude outward,
  most commonly in the lumbrosacral region.

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Vertebral Column

• Cervical Vertebrae (7)
• Thoracic Vertebrae (12)
• Lumbar Vertebrae (5)
• Sacrum (5 fused)
• Coccyx (4 fused)

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Cervical Vertebrae (7)

• Transverse processes (projections) bear
  transverse foramina, which are passageways for
  arteries leading to the brain
• Forked bifid spinous process provides attachments
  site for muscles

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Cervical Vertebrae (7)

• The Atlas
• First vertebra
• Supports and balances the head.
• Articulates with occipital condyles of the
  cranium
• The Axis
• Second vertebra
• Provides a pivot for the atlas when the head is
  turned side to side.

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Thoracic Vertebrae (12)

• Thoracic vertebrae are larger than cervical
  vertebrae.
• Facets on the side articulate with the ribs.
• Long spinous process
• Increase in size inferiorly (as you go downward).
  Adapted to bear increasing loads of body weight.

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Lumbar Vertebrae (5)

• Vertebral bodies are large and strong.
• They support more body weight than other
  vertebrae.

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Sacrum (5 fused)

• The sacrum is a triangular structure formed of
  five fused vertebrae.
• Vertebral foramina form the sacral canal.
• Part of the pelvis

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Coccyx (4 fused)

• Tailbone
• Composed of four fused vertebrae
• Forms the lowest part of the vertebral column.
• Acts as a shock absorber when a person sits.

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Intervertebral Disks

• Composed of tough outer layer of fibrocartilage
  with an elastic central mass
• Degenerates with age, loses firmness, outer layer
  thins, weakens, cracks

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Ruptured/ Herniated Disk

• Pressure from lifting may break outer layer and
  allow it to squeeze out or rupture.
• Pressure on the spinal cord or nerve causes pain,
  numbness, loss of muscular function

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Thoracic Cage

• The thoracic cage includes
• The ribs
• Thoracic vertebrae
• Sternum
• Costal cartilages (attach ribs to sternum).

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Thoracic Cage

• Supports the pectoral girdle (shoulder girdle)
  and upper limbs
• Protects viscera (thoracic cavity and upper
  abdominal cavity)
• Functions in breathing.

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Ribs

• Twelve pairs of ribs attach to the twelve
  thoracic vertebrae and articulate posteriorly
• A typical rib has a shaft, a head, and tubercles
  that articulate with the vertebrae.

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• Costal cartilages of the true ribs join the
  sternum directly (anteriorly).
• False ribs join sternum indirectly through the
  cartilages of the 7th rib.
• Floating ribs (last 2-3) do not join the sternum
  at all.

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Sternum

• Breastbone
• Located on the midline in the anterior portion
  (front) of the thoracic cage.
• The sternum consists of a manubrium (upper part),
  body and xiphoid process.
• The manubrium articulates with the clavicles.

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Sternum (breastbone)

• Red marrow in the sternum produces blood cells
  into adulthood.
• Easily reached for marrow samples in disease
  diagnosis.
• Called sternal puncture.
• Cells also sampled from iliac crest of coxal bone

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Pectoral Girdle

• Shoulder girdle
• Composed of two clavicles and two scapulae
• Forms an incomplete ring that supports the upper
  limbs and provides attachments for muscles.
• Connects bones of the upper limbs to the axial
  skeleton and aids in upper limb movement.

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Clavicles

• Collarbones
• Rod like bones located between the manubrium and
  scapulae.
• Hold the shoulders in place and provide
  attachments for muscles of upper limbs, chest,
  and back.

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Scapulae

• Shoulder blades
• Broad, triangular bones
• Articulate with the humerus of each upper limb
  and provide attachment for muscles.

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Upper Limbs

• Bones of the upper limb provide the frameworks
  and attachments of muscles
• Function in levers that move the limb and its
  parts.

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Humerus

• Arm bone
• The humerus extends from the scapula to the
  elbow.
• It articulates with the radius and the ulna at
  the elbow and with the scapula at the shoulder.

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Radius

• Forearm bone
• Located on the thumb side of the forearm between
  the elbow and wrist.
• Articulates with the humerus, ulna, and wrist.

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Ulna

• Forearm bone
• Longer than the radius
• Overlaps the humerus posteriorly.
• Articulates with the radius laterally and with a
  disk of fibrocartilage inferiorly which joins a
  wrist bone.

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Hand

• Composed of a wrist, a palm, and five fingers.
• Includes
• 8 carpal bones (wrist bones) that form a carpus
• 5 metacarpal bones (palm)
• 14 phalanges (finger bones 3/finger, 2/thumb).

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Pelvic Girdle

• The pelvic girdle consists of two coxal bones
  (hip bones) that articulate with each other
  anteriorly and with the sacrum posteriorly.
• The sacrum, coccyx, and pelvic girdle form the
  bowl-shaped pelvis.

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Pelvic Girdle

• Supports the trunk of the body
• Connects the bones of the lower limbs to the
  axial skeleton.
• Protects the urinary bladder, distal ends of the
  large intestine, and internal reproductive
  organs.

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Coxal bone

• Consists of an ilium, ischium, and pubis, which
  are fused in the region of the acetabulum
  (depression on the side). Figure 7.27 p159

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Ilium

• Hip, iliac crest
• Largest portion of the coxal bone.
• Joins the sacrum at the sacroiliac joint

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Ischium

• Lowest portion of the coxal bone.
• Supports body weight when sitting.

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Pubis

• Anterior portion of the coxal bone.
• Pubic bones are fused anteriorly at the symphysis
  pubis.

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• The female pelvis is usually wider in all
  diameters and roomier than that of the male.
  Figure 7.26 p158

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Lower Limb

• Bones of the lower limb provide frameworks of the
  thigh, leg, and foot.

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Femur

• Thigh bone
• Longest bone in the body.
• Extends from the hip to the knee.
• Articulates proximally with the coxal bone and
  distally with the tibia and the patella.

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Patella

• Knee cap
• Articulates with the femurs anterior surface.
• Located within a tendon that passes over the knee.

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Tibia

• Shin bone
• Located on the medial side of the leg
• Larger of the two lower leg bones.
• The femur and the tibia articulate with each
  other at the knee joint where the patella covers
  the anterior surface.
• Articulates with the talus of the ankle and with
  the fibula on the lateral side.

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Fibula

• Lower leg bone
• Located on the lateral side of the tibia
• More slender than the tibia.
• Articulates with the ankle but does not bear body
  weight.
• Does not enter the knee joint.
• Protrudes on the lateral side of the ankle.

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Foot

• Consists of an ankle, an instep, and five toes.
• Includes
• 7 tarsal bones (ankle bones) that form the
  tarsus
• 5 metatarsal bones (form the instep and the ball
  of the foot)
• 14 phalanges (toes).

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Foot

• Talus (one of the tarsals) moves freely where it
  joins the tibia and fibula.
• Calcaneus largest ankle bone, projects backward
  to form the heel.
• Arches
• Form longitudinally and transversely by the
  tarsals and metatarsals which are bound by
  ligaments.
• Arches provide a stable, springy base for the
  body.

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