Lecture 5 - ANP1106

Question 1

The Human Skeleton

Answer 1

206 bones in the human skeleton, comprising about 20% of body weight divided into :
Axial skeleton – Skull, vertebral column, and rib cage ( 80 bones )
Appendicular skeleton – Upper limbs & pectoral girdles plus lower limbs & pelvic girdles ( 126 bones)

Question 2

The Skull

Answer 2

• Includes cranial & facial bones united by sutures as well as the bone of the tongue (not attached to anything)
• Houses special sensory organs (sight, sound, balance, smell, and taste), paranasal sinuses, the CNS, and has 85 openings for nerves and blood vessels so that they can reach brain tissue

Question 3

Cranial Bones

Answer 3

Form the vault of the skull (space inside skull) containing 3 bony ridges dividing the cranial base internally into 3 distinct areas :
- Anterior fossa (highest)
- Middle fossa
- Posterior fossa (lowest)

Question 4

What are the 8 cranial bones ?

Answer 4

Paired parietal + temporal bones [ 4 ] & unpaired frontal, occipital, sphenoid, and ethmoid bones

Question 5

Parietal bones

Answer 5

Paired bones forming the bulk of the cranial vault on the superior & lateral aspects of the skull

Question 6

Temporal bones

Answer 6

Paired bones located just below the 2 parietal bones forming inferior and lateral aspects of the skull & cranial floor

Question 7

Frontal bone

Answer 7

Dome-shaped bone forming the anterior cranial fossa & the roof of the orbits with its supraorbital margin, supraorbital foramen (passage for blood vessels and nerve fibers), and glabella (margin above nose containing inside the left and right frontal sinuses) and it articulates with the paired parietal bones posteriorly

Question 8

Occipital bone

Answer 8

Single bone at the base of the skull forming the posterior cranial fossa and the posterior aspect of skull which attaches anteriorly to the 2 parietal bones, 2 temporal bones & sphenoid, and has the foramen magnum (a large hole at the base for passage of CNS), occipital condyles on each side of foramen magnum (sites of articulation with first cervical vertebra), and external occipital protuberance which is a projection at back of skull (more prominent in males) for the attachment of muscles

Question 9

Sphenoid

Answer 9

Articulates with all other cranial bones, forms the base of middle cranial fossa and contributes to the base of anterior cranial fossa

Question 10

Ethmoid

Answer 10

Lies deep between the orbits and the nasal cavities

Question 11

What are the 4 sutures connecting the cranial bones ?

Answer 11

Sutures may contain sutural bones which are tiny irregular bones formed by ossification centres that appeared during fetal development :
- Coronal suture between frontal bone and 2 parietal bones
- Squamous suture between parietal bone and temporal bone
- Lambdoid suture between occipital bone and 2 parietal bones
- Sagittal suture along midlne between 2 parietal bones

Question 12

What are the 3 parts of the temporal bones ?

Answer 12

Squamous part – Flattened bone from the zygomatic process to the cheekbone (zygomatic bone of face) with a mandibular fossa for articulating with condyle of the mandible (jaw)
Tympanic part – Surrounds the external acoustic meatus
Petrous part – Internal aspect of the temporal bone where it contributes to the cranial base, houses middle and inner ear cavities (sensory organs for hearing + balance), and forms mastoid process (attachment site for some neck muscles), styloid process (attachment site for muscles of the tongue and some neck muscles), and several foramina (jugular foramen, carotid canal, and internal acoustic meatus)

Question 13

What are the components of the sphenoid bone ?

Answer 13

• Central body contains sphenoid sinuses, optic foramina (canals for optic nerves), superior orbital fissure between greater & lesser wings (passage for cranial nerves producing eye movement)
• 3 projections : Greater wing, lesser wing (forms orbits and the middle and anterior cranial fossae), and pterygoid process (attachment of muscles for mastication)

Question 14

What are the components of the ethmoid bone ?

Answer 14

• Cribriform plate – Forms the roof of the nasal cavity & the floor of the anterior cranial fossa with tiny holes (olfactory foramina) for passage of olfactory nerves
• Perpendicular plate – Projects inferiorly to contribute to the nasal septum
• Crista galli – Projects superiorly to attach to the dura mater of brain
• Lateral masses – Containing ethmoid sinuses
• Medially located superior & middle nasal conchae
• Laterally located orbital plates – Contribute to the medial walls of orbits

Question 15

What are the functions of facial bones ?

Answer 15

• Form the framework of the face
• Anchor the facial muscles for expression
• Secure the teeth
• Contain the cavities for the sensory organs of sight, smell and taste
• Provide openings for passage of food and air

Question 16

What are paranasal sinuses ?

Answer 16

Paranasal sinuses in the frontal, maxillary, sphenoid, and ethmoid bones of the facial bones

Mucosa-lined, air-filled spaces that connect to the nasal cavity to warm and humidify incoming air but also to lighten the skull and enhance resonance of the voice (when your nose is blocked, you wont sound the same)

Question 17

How many bones make up the facial bones and which ones are they ?

Answer 17

14 bones of which mandible and vomer are unpaired whereas maxillae, zygomatic, nasal, lacrimal, palatine and inferior conchae are paired

• Mandible is the lower jaw bone (strongest and largest bone of the face)
• Maxillary bones are fused medially
• Zygomatic bones are the cheekbones that articulate with zygomatic processes of maxilla, frontal bone, and temporal bone and also contribute to inferolateral margins of the orbit
• Nasal bones are 2 tiny rectangular bones that fuse medially to form bridge of nose and articulate with the frontal bone superiorly and maxillary bones laterally
• Lacrimal bones are 2 fingernail-shaped bones in the anterio-medial portion of the orbit, each with a depression (lacrimal fossa) for the lacrimal sac, and articulates with the frontal bone, ethmoid bone, and maxillae
• Palatine bones are 2 L-shaped bones where the horizontal plates form part of the hard palate and the vertical plates form the nasal cavity and orbit
• Vomer is a single thin bone forming the nasal septum
• Inferior nasal conchae are thin curved bones that project medially and forms the largest of 3 pairs of conchae (the other 2 are the middle and superior nasal conchae of the ethmoid bone)

Question 18

Orbit

Answer 18

Zygomatic, frontal, maxilla, ethmoid, lacrimal, sphenoid, and palatine bones
- Forms sockets of eye

Question 19

Mandible

Answer 19

Has a body containing the chin + left & right rami extend from the body at the mandibular angle and contain the following bone markings :
- Mandibular notch
- Coronoid process (for insertion of temporalis muscle)
- Mandibular condyle
- Alveolar margin (contains tooth sockets)
- Mandibular foramina (passage of nerves to teeth in lower jaw)
- Mental foramina (blood vessels and nerves to chin and lower lip)

Question 20

Maxillary Bones

Answer 20

• Have alveolar margins to hold teeth of the upper jaw
• Palatine processes projecting posteriorly to form the anterior 2/3 of hard palate

Contain the following bone markings :
- Incisive fossa (passage of blood vessels and nerves)
- Frontal processes (articulates with frontal bone)
- Zygomatic processes (articulates with zygomatic bone)
- Maxillary sinus in main portion of bone on each side (common site of infection)

Question 21

Tongue Bone

Answer 21

Contains the hyoid bone (only bone of the body that does not articulate with any other bone) that is horseshoe-shaped with a body and 2 pairs of horns to support the tongue and other muscles for speaking, eating, and swallowing

Question 22

What is the vertebral column ?

Answer 22

Includes 32 - 33 bones (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 3 or 4 coccygeal) forming a column of 70 cm long in an adult of average height composed of 24 mobile bones to allow movement and the remaining 8-9 fuse to form 2 composite bones (sacrum and coccyx)

Question 23

What are the 3 main functions of the vertebral column ?

Answer 23

• Weight-bearing
• Anchoring muscles & ligaments
• Protecting of the spinal cord

Question 24

Describe the normal curvature of the vertebral column ?

Answer 24

The normal curvature alternates between concave (lateral view curves anteriorly) and convex (lateral view curves posteriorly) :
- Cervical (concave – curves inwards)
- Thoracic (convex – curves outwards, where it is exaggerated in kyphosis)
- Lumbar (concave where it is exaggerated in lordosis)
- Sacral (convex) but in scoliosis the curvature is lateral instead of anterior or posterior

Question 25

Abnormal Curvatures of the Spine

Answer 25

Scoliosis – Curvature of the spine laterally
Kyphosis – Exaggerated thoracic convex curvature
Lordosis – Concave curvature of the lumbar area, can occur temporarily with pregnancy

Question 26

What are the supporting elements of the vertebral column ?

Answer 26

• Ligaments
• Intervertebral discs

Question 27

Ligaments

Answer 27

Major supporting ligaments are anterior (wide and attached to bony vertebrae and discs to prevent hyperextension of spine – if u bend backwards, this is stretched to prevent going too far backwards) and posterior (narrow and attaches only to the discs to prevents hyperflexion of spine – forward flexion) longitudinal ligaments forming continuous bands down the front and back of vertebral bodies from the neck to the sacrum

Question 28

Intervertebral discs

Answer 28

Form 25% of the vertebral column length

Allow mobility of vertebral column & provide cushioning (shock absorbers) between bony vertebral bodies

• Each disc is circular with a central nucleus pulposus (elastic, compressible – soft jelly like) and an annulus fibrosus around the periphery (attached to adjacent vertebrae – very strong fibrous tissue packaging nucleus) which is largest in cervical and lumbar regions

Question 29

How does a herniated disk occur ?

Answer 29

Occurs when a portion of the nucleus pulposus pushes through a crack in the annulus and then may compress a spinal nerve – Excessive pressure applied causes break in annulus fibrosis so now jelly like fluid of nucleus pulposus can push onto dorsal nerve root → compresses root to cause pain, losing sense of touch