Anatomy and Physiology

Skeletal System part II

Skeletal Organization

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

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

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

• 206 bones in an adult skeleton

Fig 7.12 Occipital condyle Condyle = A rounded process that usually articulates with another bone

Fig 7.27 Iliac crest Crest = A narrow, ridgelike projection

Fig 7.16 and 7.17 Rib facet of thoracic vertebrae

Facet = A small, nearly flat surface

Fig 7.15 Anterior fontanelFontanel = A soft spot in the skull where membranes cover the space between bones

Fig 7.12 Foramen magnumForamen = A opening through a bone that usually is a passageway for blood vessels, nerves, or ligaments

Fossa = a relatively deep pit or depressionFig 7.23 Olecranon fossa of humerus

Fig 7.29 Fovea capitus of femur Fovea= a tiny pit or depression

Fig 7.23 Head of humerus Head = An enlargement on the end of a bone

Fig 7.11 External auditory meatus Meatus = A tubelike passageway within a bone

Fig 7.11 Mastoid process Process = A prominent projection on a bone

Fig 7.14 Frontal sinus Sinus = A cavity within a bone

Fig 7.22 Spine of scapula Spine = A thornlike projection

Fig 7.11 Lambdoidal suture Suture = An interlocking line of union between bones

Fig 7.29 Greater trochanter of femur Trochanter= a relatively large process

Fig 7.23 Greater tubercle of humerus Tubercle= a small, knoblike process

Fig 7.24 Radial tuberosity of radius

Tuberosity = a knoblike process usually larger than a tubercle

Skull

• The skull consists of twenty-two bones.– 8 cranial bones– 14 facial bones (13 + 1 mandible)

Skull

• Cranium (braincase)– The cranium encloses and protects the

brain– Surface of the cranium provides

attachments for muscles used in chewing and head movements

– Some cranial bones contain air-filled paranasal sinuses.• Sinuses are lined with mucous membranes and

are connected to the nasal cavity

• Sinuses reduce the skull’s weight and increase voice intensity by resonance

Cranial bones include: • Frontal bone• Parietal bones• Occipital bone• Temporal bone• Sphenoid bone• Ethmoid bone

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

Facial Skeleton

• Facial bones – Form the basic shape of the face – Provide attachments for muscles that move

the jaw– Control facial expressions

Facial SkeletonFacial bones include: – Maxillae

– Palatine bones– Zygomatic bones– Lacrimal bones– Nasal bones– Vomer bone– Inferior nasal

conchae– Mandible

Mandible

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

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

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

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

Hyoid Bone

• Located in the neck between the lower jaw and the larynx

• Supports tongue and attachment site for muscles used during swallowing

Vertebral Column

• Backbone or Spine• The vertebral column extends from the

skull to the pelvis

Vertebral Column

• Protects the spinal cord which passes through the vertebral canal

• Supports the head and trunk

Vertebral Column (backbone)

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

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 intervertebralforamina (openings) through which spinal nerves pass.

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.

Vertebral Column

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

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

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.

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.

Lumbar Vertebrae (5)

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

other vertebrae.

Sacrum (5 fused)

• The sacrum is a triangular structure formed of five fused vertebrae.

• Vertebral foramina form the sacral canal.

• Part of the pelvis

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.

Intervertebral Disks

• Composed of tough outer layer of fibrocartilage with an elastic central mass

• Degenerates with age, loses firmness, outer layer thins, weakens, cracks

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

Thoracic Cage

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

Thoracic Cage

• Supports the pectoral girdle (shoulder girdle) and upper limbs

• Protects viscera (thoracic cavity and upper abdominal cavity)

• Functions in breathing.

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.

• 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.

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.

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

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.

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.

Scapulae

• Shoulder blades• Broad, triangular bones• Articulate with the humerus of each

upper limb and provide attachment for muscles.

Upper Limbs

• Bones of the upper limb provide the frameworks and attachments of muscles

• Function in levers that move the limb and its parts.

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.

Radius

• Forearm bone• Located on the thumb side of the

forearm between the elbow and wrist.• Articulates with the humerus, ulna, and

wrist.

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.

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).

Pelvic Girdle

• The pelvic girdle consists of two coxalbones (hip bones) that articulate with each other anteriorly and with the sacrum posteriorly.

• The sacrum, coccyx, and pelvic girdle form the bowl-shaped pelvis.

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.

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

Ilium

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

Ischium

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

Pubis

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

symphysis pubis.

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

Lower Limb

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

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.

Patella

• Knee cap• Articulates with the femur’s anterior

surface. • Located within a tendon that passes

over the knee.

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.

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.

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).

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 tarsalsand metatarsals which are bound by ligaments.

– Arches provide a stable, springy base for the body.