Forms the longitudinal axis of the body Divided into three parts

◦ Skull- protects the brain◦ Vertebral column – protects the spinal column◦ Bony thorax-protects thoracic cavity (heart &

lungs)

The Axial Skeleton

The Axial Skeleton

Figure 5.6a

The Axial Skeleton

Figure 5.6b

Two sets of bones◦ Cranium◦ Facial bones

Bones are joined by sutures- interlocking joints; immovable joints that connec bones of skull

Only the mandible is attached by a freely movable joint

The Skull

Suture Bones they connect

Sagittal 2 parietal bones

Coronal Parietals meet frontal bone

Squamous Temporal meets parietal

Lamboid Occipital meets parietal

Major Sutures of the skull

1. Frontal2. Sphenoid3. Ethmoid4. Right Parietal5. Left Parietal6. Right Temporal7. Left Temporal8. Occipital

Bones of the Cranium

Facial Bones1. Maxillae2. Palantine3. Zygomatic4. Lacrimal5. Nasal6. Vomer7. Inferior Nasal Conchae8. Mandible

Human Skull, Lateral View

Figure 5.7

Bone forming anterior cranium

Has greater and lesser wings

Superior and inferior nasal conchae are part of this boneIts “holey plate allows olfactory fibers to pass

Allows tear ducts to pass

Cheek bone

Forms most of hard palateUpper jaw

Boney skeleton of the nose

Site of external auditory meatus

Bone pair united by sagittal suture

Human Skull, Superior View

Figure 5.8

**forms a plateau across the width of the skull

•Has greater and lesser wings•Contains a “saddle” that houses the pituitary gland

Human Skull, Inferior View

Figure 5.9

Site of jugular foramen and carotid canal

•Its oval-shaped protrusions articulate with the atlas•Spinal cord passes through opening

Posterior roof of mouth

Inferior part of nasal septum

Forms most of hard palate

Human Skull, Anterior View

Figure 5.11

•Contain alveoli bearing teeth•Facial bone that contains a sinus

•Forms the chin•Contain alveoli bearing teeth

Contains a paranasal sinus

Contains a paranasal sinus

Contains a paranasal sinus

Inferior part of nasal septum

Sagittal suture

(Greater wing)Squamous sutrue

Hollow portions of bones surrounding the nasal cavity

Functions of paranasal sinuses1. Lighten the skull2. Give resonance and amplification to voice

Paranasal Sinuses

Paranasal Sinuses

Figure 5.10a

Paranasal Sinuses

Figure 5.10b

The only bone that does not articulate with another bone

Serves as a moveable base for the tongue Aids in swallowing and speech

The Hyoid Bone*not really a skull bone

The Hyoid Bone

Figure 5.12

The Fetal Skull aka BIG HEAD The fetal skull is large compared to the

infant’s total body length◦ Fetal skull is 1/4th total body length◦ Adult skull is only 1/8th total body length

AdolescenceEpiphyseal plates become ossified and long bone growth ends

The Fetal Skull

Figure 5.13a

The Fetal Skull

Figure 5.13b

Face is smaller in proportion to cranium

Growth (ossification) center:conical projection on some cranial bones

Developmental Aspects of the Skeletal System Fontanels—fibrous membranes connecting

the cranial bones◦ Allows skull to be compressed during birth and

allows for brain growth during late fetal life At birth, the skull bones are incomplete Bones are joined by fibrous membranes

called fontanels Fontanels are completely replaced with

bone within two years after birth

Skeletal Changes Throughout Life Fetus

◦ Long bones are formed of hyaline cartilage

◦ Flat bones begin as fibrous membranes

◦ Flat and long bone models are converted to bone

Birth◦ Fontanels remain until around

age 2

Ossification Centers in a 12-week-old Fetus

Skeletal Changes Throughout Life Size of cranium in relationship to body

◦ 2 years old—skull is larger in proportion to the body compared to that of an adult

◦ 8 or 9 years old—skull is near adult size and proportion

◦ Between ages 6 and 11, the face grows out from the skull

Skeletal Changes Throughout Life

Figure 5.33a

Between ages 6 and 11, the face grows out from the skull

The Vertebral Column Each vertebrae is given a name according

to its location◦ There are 24 single vertebral bones separated by

intervertebral discs - made up of fibrocartilage Seven cervical vertebrae are in the neck Twelve thoracic vertebrae are in the chest region Five lumbar vertebrae are associated with the lower

back

Herniated disc= a slipped disc; protruding cartilage from vertebra. Causes pain and numbness

The Vertebral Column Nine vertebrae fuse to form two composite

bones◦ Sacrum- five components; fused◦ Coccyx- tail bone

The Vertebral Column

Figure 5.14

The Vertebral Column The spine has a normal curvature

◦ Primary curvatures are the spinal curvatures of the thoracic and sacral regions…like a c Present from birth

◦ Secondary curvatures are the spinal curvatures of the cervical and lumbar regions…like an s Develop after birth

The Vertebral Column C shaped spine

Figure 5.15

The Vertebral ColumnAbnormal spinal curvatures (scoliosis and lordosis) are often congenital

Figure 5.16

A Typical Vertebrae, Superior View

Figure 5.17

Regional Characteristics of Vertebrae

Figure 5.18a

Atlas lacks a bodyPivots with C2

Axis articulates with the occipital condyles

Regional Characteristics of Vertebrae

Figure 5.18b

Forked spinous process

Regional Characteristics of Vertebrae

Figure 5.18c

Bear facets for articulation with ribs; form part of the bony thoracic cage

Regional Characteristics of Vertebrae

Figure 5.18d

Vertebrae with blocklike body and short stout spinous process

Sacrum and Coccyx Sacrum

◦ Formed by the fusion of five vertebrae◦ Forms a joint with the hip bone

Coccyx◦ Formed from the fusion of three to five vertebrae◦ “Tailbone,” or remnant of a tail that other

vertebrates have

Sacrum and Coccyx

Figure 5.19

The Bony Thorax Forms a cage to protect major organs-cone

shaped Consists of three parts

◦ Sternum◦ Ribs

True ribs (pairs 1–7) False ribs (pairs 8–12) Floating ribs (pairs 11–12)

◦ Thoracic vertebrae

The Bony Thorax

Figure 5.20a

Kyphosis

Scoliosis

Lordosis is a condition that causes the spine to curve towards the body at an exaggerated rate. This curvature makes the individual appear to have a swayback.

Signs of lordosis include a prominent protrusion of the buttocks. An inflexible spine in the affected area signals a severe case of lordosis. Individuals with lordosis and a flexible spine may require no treatment beyond physical therapy. Treatment for lordosis with an inflexible spine includes using a brace and possible surgery.

Lordosis