Chapter 8 skeletal system

Bones in the adult and child body

Adult: 206 bones (some variation within bones that form within tendons (sesamoid), and bones that deveelop in skull suture lines (sutural bones).

At birth 270 bones but number decreases with fusion.

ex- ilium, ischium, and pubis fuse to form a hip bone.

Paranasal cavities

Frontal, sphenoid, ethmoid, and maxiallary

air filled cavities connected to nasal cavity and lined by mucous membranes.

cranial bones

There are eight cranial bones:

1 frontal

2 parietal

2 temporal

1 occipital

1 sphenoid

1 ethmoid

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ehtmoid bone

The ethmoid bone is located between the eyes

Contributes to medial wall of orbit, walls and roof of nasal

cavity, and nasal septum

The Mandible

Structure of each Y-shaped ramus:

Posterior branch is condylar process containing mandibular

condyle for articulation with temporal bone to form

temporomandibular joint (TMJ)

Anterior branch called the coronoid process2attachment site for

temporalis muscle involved in mastication

Mandibular notch between the two processes

Mandibular foramen2opening below notch on medial surface of

ramus; allows passage of nerves and vessels that supply lower

teeth

Hyoid bone

Slender U-shaped bone between chin and larynx

Does not articulate with any other bone

Suspended from styloid processes of skull

fractured hyoid is sign of strangulation

vertebral column

The vertebral column (spine) is a flexible chain of 33

vertebrae with fibrocartilaginous intervertebral discs

between them

protects spinal cord

Supports skull and trunk and allows for their movement

Protects spinal cord

Absorbs stresses of movements

Provides attachments for limbs, thoracic cage, and postural

muscles

vertebral column

7 cervical vertebrae in the neck

12 thoracic vertebrae in the chest

5 lumbar vertebrae in lower back

5 sacral vertebrae at base of spine

4 coccygeal vertebrae (tail bone_

reason for most variations in adult bone number?

Variations in number of vertebrae occur in 1 in 20 people.

Generally due to differences in the number of fused

vertebrae in inferior part of spine.

Kyphosis

concave in anterior direction (curved outward

toward back)

Lordosis

concave in posterior direction (curved outward

toward front)

Beyond 3 years of age, the vertebral column has four bends

Cervical lordosis, thoracic kyphosis, lumbar lordosis, pelvic

kyphosis

scoliosis

most common in teenagers.

curves laterally/ deviates from midsaggital plane

hyperkyphosis

most common in older women

cervical goes from lordosis to kyphosis

Hyperkyphosis—an excessive forward curvature of the thoracic (mid-to-upper) spine—is most common in older adults, particularly postmenopausal women. [1, 2]

hyperlordosis

common in pregnant women

Hyperlordosis is an excessive inward curvature of the lower back (the lumbar spine) or, less commonly, the neck (the cervical spine)

. While a healthy spine naturally curves inward in these regions to absorb shock and support weight, an exaggerated curve creates a distinct "swayback" appearance.

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superior view vertebra

posterior view vertebrae

left lateral view vertebrae

Intervertebral disc-

cartilaginous pad located between

bodies of adjacent vertebrae

Consists of two parts:

Nucleus pulposus-inner gelatinous mass

Anulus fibrosus-outer ring of fibrocartilage

Functions: bind vertebrae together, support weight of the

body, absorb shock

Herniated disc

causes pinched nerve: The spinal canal and the tiny exit holes for nerves (the foramina) are already highly cramped, narrow spaces. When the disc material bulges into this narrow pathway, it physically collides with and squishes the nearby spinal nerve root. we get chemical burn too- molecules body doesnt recognize leads to inflammatory response

ruptured or slipped sic puts painful pressure on spinal nerve or spunal cord

True ribs

(vertebrosternal) ribs (ribs 1 to 7)- each rib has its

own costal cartilage connecting it to the sternum

False ribs

(ribs 8 to 12)-each rib lacks an independent

cartilaginous connection to sternum

vertebrochondral ribs

Ribs 8 to 10 have associated cartilages that merge with that of rib 7;

also called ?

floating (vertebral) ribs

Ribs 11 to 12 do not connect to cartilage at all, so they are also

called

humerus

The humerus is the only bone in the brachium

Features of the proximal end:

Head-hemispherical projection that articulates with the glenoid

cavity of scapula

Anatomical neck-groove bordering head

Greater and lesser tubercles-bumps for muscle attachments

Intertubercular sulcus-groove between tubercles accommodates

tendon of biceps muscle

Surgical neck-narrowing just distal to the tubercles; common

fracture site

Deltoid tuberosity-rough area on lateral surface of shaft;

attachment site for deltoid muscle

superior/proximal end of right humerus

distal/inferior view of right humerus

The Carpal Bones

8 carpal bones: Allow movements of flexion, extension, abduction, and

adduction

Arranged in two rows of four bones each

Proximal row: scaphoid, lunate, triquetrum, and pisiform

Pisiform is a sesamoid developed by age 9 to 12 in tendon of flexor carpi

ulnaris muscle

Distal row: trapezium, trapezoid, capitate, and hamate

peter told lisa she has curly toes today

hamate