Lecture 09

Axial Skeleton

-forms the long axis of the body -includes: skull, vertebral column, rib cage -bones involved with protecting, supporting, and carrying other body parts

Appendicular Skeleton

-bones of the upper and lower limbs & girdles -includes hip and shoulder -bones involved in locomotion

The Skull

-most complex bony structure in the body -composed of 22 bones *Cranial bones (8 bones) *Facial bones (14 bones) -most are flat bones -bones are united together by sutures *interlocking joints with saw-toothed or serrated appearances *exception is mandible which is freely moving

The Cranium

-encloses the brain and furnishes the attachment sites for the head & neck muscles -single and paired bones -divided into 2 parts (Cranial vault & Cranial base)

Single bones of the cranium

-frontal -occipital -ethmoid -sphenoid

Paired bones of the cranium

-temporal -parietal

Cranial vault

-round portion that makes up the superior, lateral, and posterior portions of the skull

Cranial base

-makes up the floor or interior portion of the skull -Foramen magnus: where spinal cord exits the cranium

Cranial Fossae

-contoured depressions that make up the floor of the cranium -Anterior cranial fossa -Middle cranial fossa -Posterior cranial fossa

Anterior cranial fossa

-frontal bone, ethmoid bone, and sphenoid bone -supports the frontal lobe

Middle cranial fossa

-sphenoid bone and temporal bone -supports the temporal lobe and the pituitary gland

Posterior cranial fossa

-temporal bone and occipital bone -supports the cerebellum and part of the brainstem

Cranial Sutures

-immovable joints that form boundaries between the cranial bones -4 major sutures: *Coronal suture *Lambdoid suture *Sagittal suture *Squamous suture

Coronal suture

-extends laterally across the superior surface along the coronal plane -articulation between frontal and parietal bones

Lambdoid suture

-arc across the posterior surface of the skull -looks like a lambda (l) -articulation between parietal and occipital bones

Sagittal suture

-extends between coronal and lambdoid sutures along the midsagittal plane -articulates between the paired parietal bones

Squamous suture

-one on each side of the skull -articulates between the temporal and parietal bone (on a side)

Facial Skeleton

-bones that form the framework for the face -single bones -paired bones

Single bones of facial skeleton

-mandible -vomer

Paired bones of facial skeleton

-nasal bones -lacrimal bones -zygomatic bone -palatine bones -maxilla -inferior nasal concha

Function of facial skeleton

-contain or form cavities for the special sense organs (sight, smell, taste) -turbinate air -provides openings for the passage of air and food -securing teeth -anchor facial muscle

Cavities of skull

-cranial -orbital -nasal -oral

Cranial cavity

-largest cavity -surrounds the brain

Orbital cavities

-contain eyeballs, blood vessels, muscles, nerves, and lacrimal glands that secrete tears -formed by frontal, sphenoid, ethmoid, zygomatic, palantine, maxilla, and lacrimal bones

Nasal cavity

-contains passages for air and special sensory neurons for smell; it is considered the first part of the respiratory tract -divided by the septum (formed by vomer & ethmoid bone) -formed by sphenoid, ethmoid, palantine, nasal bones, maxilla, & inferior nasal concha

Oral cavity

-contains teeth, tongue, a passage for both food and air, and most of the salivary glands -formed by mandible and maxilla

Nasal and paranasal sinuses

-air filled chambers within the bones of the skull -located around the nasal cavity *4 paranasal sinuses *named for which bone they are located -possess small openings between sinuses and nasal cavity -mucus-lined and air-filled *air moves in from nasal cavity *mucus drains out to nasal cavity

Function of nasal and paranasal sinuses

-help to warm & humidify air -lighten the skull -enhance resonance of the voice

Hyoid bone

-found in the anterior neck region -no direct articulations with any other bones *position maintained by a combination of ligaments and muscles

Lesser and greater horns

-2 pairs of projections in hyoid bone -important sites of attachment for muscles involved in swallowing and speech production

Vertebral column

-4 divisions & 4 curvatures *Cervical *Thoracic *Lumbar *Sacral *Coccygeal (letter designates the type of vertebrae and a subscripted number its position)

Cervical vertebrae

-7 -concave curvature

Thoracic vertebrae

-12 -convex curvature

Lumbar vertebrae

-5 -concave curvature

Sacral vertebrae

-5 -vertebrae are fused, called the sacrum -convex curvature

Coccygeal vertebrae

-4 -vertebrae are fused, called the coccyx

Why does the spine curve?

-provides flexibility & increased resilience -better supports the weight of body -functions more like a spring

Body (structure of vertebrae)

-weight-bearing portion -located anteriorly

Vertebral foramen (structure of vertebrae)

-space between the body & arch -make up the vertebral canal

Vertebral arch (structure of the vertebrae)

-composite structure -located posteriorly -composed of 2 pedicles and 2 laminae

Spinal process

-single -extends anteriorly

Articular processes

-2 pairs -extend superiorly & inferiorly

Transverse processes

-one pair -extend laterally

Intervertebral discs

-reside between the vertebrae to provide cushioning -2 parts: *Anulus fibrosis *Nucleus pulposus

Anulus fibrosis

-outer portion -composed of collagen fibers and fibrocartilage -limits the expansion of the nucleus pulposus

Nucleus pulposus

-inner portion of the disc -elastic and compressible

Cervical vertebrae

-Body shape & size: *small and oval *C1 lacks a body *C2 has the dens on the superior surface of its body Vertebral foramen shape: triangular Transverse processes: contain transverse foramina Spinous processes: *most are fork-shaped *C1 lacks a spinous process

Thoracic vertebrae

-Body shape & size: *larger and heart-shaped *contain costal facets Vertebral foramen shape: circular Transverse processes: *long *contain articular facets for ribs Spinous processes: *long *point inferiorly

Lumbar vertebrae

-Body shape & size: *largest *kidney-shaped Vertebral foramen shape: -flattened triangular Transverse processes: *short *no facets or foramina Spinous processes: *thick *point posteriorly

Sacrum

-formed by 5 fused vertebrae -superior articular process connects to hip -possesses foramen for blood vessels & spinal nerves to pass through

Coccyx

-formed by 4 fused vertebrae *(occurs around age 25) -attachment site for several ligaments

Thoracic cage: Sternum

-breastbone -stabilizes the thoracic cage -protects the heart, vena cava, and thymus -made of 3 bones: *Manubrium *Body *Xiphoid process

Manubrium

-articulates with clavicle and ribs -part of the sternum

Body

-articulates with ribs -part of sternum

Xiphoid process

-initially composed of hyaline cartilage, ossifies by age 40 -attachment point for the abdominal muscles -part of sternum

Thoracic cage: Ribs

-all attach posteriorly to the thoracic vertebrae -true & false ribs

True ribs

-ribs 1-7 -attach directly to sternum

False ribs

-ribs 8-12 -ribs 8-10 attach to rib 7 -ribs 11 & 12 are floating ribs

Rib structure

-bowed flat bone *Shaft *Head *Neck *Angle *Tubercle

Shaft

-comprises the bulk of rib

Head

-articulates with the thoracic vertebrae at the costal groove -divided into the superior and inferior articular facets

Neck

-area between the head and tubercle

Angle

-the point where the ribs curves toward the sternum

Tubercle

-articulates with the transverse process of the vertebrae

The pectoral girdle: Clavicle

-composed of 2 bones: Clavicle and Scapula (aka collar bone) -located anteriorly -attachment point for many muscles -acts as a brace to hold the arms and scapula away from the body -Sternal end *articulates with the manubrium of the sternum -Acromial end *articulates with the acromion of the scapula

The pectoral girdle: Scapula

(aka shoulder blade) -located posteriorly *attached to the axial skeleton via articulation with the clavicle and various muscles -Dorsal surface possesses ridge called the spine *ends at the acromion which articulates with the clavicle -Lateral border *Glenoid cavity serves as the site of articulation with humerus -3 fossae for muscle attachment *(Ventral surface) - subscapular *(Dorsal surface) - supraspinous & infraspinous

Humerus

-articulates with scapula to form the shoulder *head *tubercules (greater & lesser) *deltoid tuberosity articulates with ulna and radius to form the elbow *distal end *capitulum *trochlea *epicondyles (lateral & medial)

Head of humerus

-proximal end -fits into the Glenoid cavity

Tubercules (Greater & Lesser)

attachment sites for the rotator cuff

Deltoid tuberosity

attachment for the deltoid muscle

Capitulum

-lateral -articulates with the head of the radius

Trochlea

-medial -articulates with the trochlear notch of the ulna

Epicondyles (lateral & medial)

-attachment sites for muscles -ulnar nerve travels posterior to the medial epicondyle

Forearm

-includes the ulna and radius *connected via interosseous membrane -ulna -radius

Ulna

-medial bone -slightly longer than the radius -trochlear notch -olecranon -styloidprocess: connects to the wrist

Trochlear notch

forms the elbow joint with humerus

Olecranon

bony end of the elbow

Radius

-lateral bone -styloid process: connects to the wrist

Carpal bones

-wrist bones -8 per wrist -closely united by ligaments -2 rows, lateral to medial *proximal row *distal row

Proximal row of carpal bones

-Scaphoid, Lunate, Triquetrum, Pisiform (Some Lunatics Try Positions)

Distal row of carpal bones

-Trapezium, Trapezoid, Capitate, Hamate (That They Can't Handle)

Hands

-palms -fingers

Palms

-5 metacarpal bones -thumb or pollux (l) to Pinky (V) *lateral to medial -heads of metacarpals make up the knuckles

Fingers

-14 phalanges (s. phalanx) -Thumb (I) has 2 phalanges (proximal & distal) -Index finger (II) to Pinky (V) each have 3 phalanges each (proximal, middle, and distal)

Pelvic Girdle

-attaches lower limbs to the axial skeleton -refers to the pairs of os coxae (hip) bones *start out as 3 pairs of bones, but fuse age 13-15 3 bones -ilium (superior) -ischium (inferior) -pubis (anterior) -Obturator foramen -articulates with the femur at the acetabulum

Ilium

-superior Iliac crest: protrudes, regarded as hip -serves as an attachment point for muscles of the trunk, hip, and thigh -articulates with the sacrum at the sacroiliac joint

Ischium

-inferior -bear weight of the body when sitting via the paired ischial tuberosities

Pubis

-anterior -jointed together by the pubic symphysis (fibrocartilage disc)

Obturator foramen

-formed by the pubis and ischium -allows blood vessels and nerves to pass to lower limbs

Acetabulum

-the point of fusion for all 3 bones

The thigh: femur

-largest, strongest, and longest bone in body (~1/4th size of height) -covered with bulky muscles -head articulates with hip -shaft moves medially allowing knees to be closer together towards the body's center of gravity *gluteal tuberosity is the attachment site for the gluteus maximus muscle -condyles (lateral & medial) articulate with the tibia to form the knee joint -trochanters *greater projects laterally *lesser projects posteromedially *processes that serve as insertion sites for the gluteal and thigh muscles -patella (kneecap) *enclosed in the quadriceps femoris tendon *protects the knee joint *improves the leverage of the thigh muscle

Lower leg

-tibia -fibula

Tibia

-larger of the 2 bones -head articulates with the femur -located medially -bears the weight of the body & transfers it to the foot -articulates with the fibula & talus to form ankle *medial malleolus: bony process that forms the inside ankle bone

Fibula

-smaller of the two bones -head articulates with the tibia -located laterally -articulates with the tibia & talus to form ankle *lateral malleolus: bony process that forms the outside ankle bone & provides lateral stability

Tarsal bones

-ankle bones -seven bones located distal to the lower leg *1st group (superior to inferior): Talus, Calcaneus *Middle medial loner: Navicular *Distal row (medial to lateral): Medial cuneiform, Intermediate cuneiform, Lateral cuneiform, Cuboid -2 bones of interest *Talus (ankle) - articulates tibia and fibula *Calcaneus (heel) - under the talus, attached to the Achilles tendon (Proximal group): Tall Californian (Middle loner): Navy (Distal row): Medical Interns Love Cuties

Metatarsals

-5 long bones located distal to the tarsal bones and proximal to the phalanges -enumerated (I to V) *medial to lateral

Phalanges

-Hallux: big toe *has only a proximal and distal phalanx -each of the other toes has 3 phalanx (proximal, middle, and distal) just as fingers do

Arches of the foot

-provide strength to the foot -allows for there to be some give in the foot -2 longitudinal arches (medial & lateral) -1 transverse arch -maintained by the attachment between the bones, ligaments, and tendons

Medial longitudinal arch

-highest of the 3 arches -prevents the medial side of the foot from touching the ground -gives our footprint the characteristic shape -extends from ball of foot (great toe) to heel

Lateral longitudinal arch

-not as high as the medial arch -contributes to our footprint -extends from little toe to the heel

Transverse arch

-runs perpendicular to the longitudinal arch -formed by the distal row of the tarsal bones