Chapter 7 Skeletal Division PDF

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Summary of notes which follows the course outline. ...

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7.1 Divisions of the Skeletal System Axial Skeleton 

Bones that are on the longitudinal (vertical line that runs through the middle of the body) axis of the human body.

Appendicular Skeleton 

Consists of upper and lower limbs, bones forming gridles that connect limbs to the axial skeleton.

7.2 Types of Bones 

Five main types: long, short, flat, irregular, and sesamoid.

1. Long Bones    

Greater length than width, consists of a shaft, variable number of epiphyses (ends). Slight curve for strength (more distribution of weight). Consists mostly of compact bone tissue in the diaphyses, and spongy bone tissue in the epiphyses. Femur (thigh bone), tibia and fibula (leg bones), humerus (arm bone), ulna and radius (forearm bones), phalanges (finger and toe bones).

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2. Short Bones   

Cubed-shape, equal length and width. Consists of spongy tissue except on the surface (thin layer of compact bone tissue). Carpal (wrist), tarsal (ankle).

3. Flat Bones   

Thin, two parallel plates of compact bone tissue, and a middle spongy bone tissue. Considerable protection and areas for muscle attachment. Cranial bones, sternum and ribs, scapulae.

4. Irregular Bones   

Complex, irregular shapes. Vary in spongy and compact bone tissue. Vertebrae (backbones), hip bones, facial bones, calcaneus (heel bone).

5. Sesamoid Bones    

Develop in tendons where there is significant friction, tension, physical stress. Vary from each person, not completely ossified, and only a few millimeters in diameter (except kneecaps which are present in everyone). Protects tendons from excessive wear and tear. Change direction of pull of tendon, improving mechanical advantage. Palms, soles

Additional bone, which is based on location and not shape. 6. Sutural Bones 

Small bones located in sutures (joints) between certain cranial bones.

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7.3 Bone Surface Markings Surface Markings    

Structural features adapted for specific functions. Develops as a person age, which results in raised or roughened areas. Depression in a bone is caused by compression. Two types: o Depressions and openings: allow passage of soft tissues or form joints. o Processes: projections or outgrowths which help form joints or attachment points for connective tissue.

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*KNOW THE MARKING AND DESCRIPTION (NO EXAMPLES NECESSARY) *

7.4 Skull Cranial Bones – Frontal Bone 

Forehead, roof of the orbits (eye sockets), anterior part of cranial floor.

Cranial Bones – Parietal Bones

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Cranial Bones – Temporal Bones

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Cranial Bones – Occipital Bone

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Cranial Bone – Sphenoid Bone

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Cranial Bone – Ethmoid Bone

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Facial Bones – Mandibles

Nasal Septum

Orbits

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Sutures and Fontanels

Sinuses (Paranasal Sinus)

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Hyoid Bone 

Located in anterior neck, supports the tongue, provides attachment sites for tongue muscles.

Vertebra and Normal Curves

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Intervertebral Disc 

Nucleus Pulposus is the spongy, middle later of the disc.

Parts of Typical Vertebra 

Vertebral Foramen is for one vertebrae, while the canal is all the vertebral foramen stacked.

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Regions of Vertebral Columns Cervical Vertebrae (C1 – C7)

Thoracic Vertebrae (T1 – T12)

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Lumbar Vertebrae (L1 – L5) 

Projections are short and thick, as the majority of the body weight is supported by the lumbar vertebrae.

Sacrum and Coccyx

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Sternum

Ribs

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Disorders Herniated Disc  

Nucleus pulposus protrude into adjacent vertebral bodies due to weakening of ligaments of the disc. Nucleus pulposus exerts pressure on the spinal nerve which results in weakness and pain.

Abnormal Curves of the Vertebral Column 1. Scoliosis  Lateral bending of the vertebral column, usually the thoracic region.  Results from malformed vertebrae, chronic sciatica, poor posture, one leg shorter than the other.  Treatment includes back brace, physical therapy, surgery.

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2. Kyphosis  Increase curve of the thoracic curve which produces a hunchback look.  Tuberculosis of the spine, vertebral bodies partially collapse causing the bending.  Caused by degeneration of intervertebral disc. Common in females with advanced osteoporosis.

3. Lordosis  Increase in the lumbar curve of the vertebral column.  Caused by increased weight of the abdomen as in pregnancy, obesity, poor posture, rickets, osteoporosis, or tuberculosis of the spine.

Spina Bifida     

Defect of the vertebral column in which the laminae of L5 and/or S1 fail to develop normally and unite at the midline. Protrusion of meninges and/or spinal cord through the defect in the laminae, which causes a cystic like sac to protrude from the backbone. Spina bifida occulta – least serious form Spina bifida cystica – if there is a cystic like sac (majority of them). Spina bifida with meningocele – sac contains meninges from spinal cord and cerebrospinal fluid. 18

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Spina bifida with meningomyelocele – spinal cord and/or its nerve roots are in the sac. Caused by low levels of vitamin b during pregnancy.

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