Chapter 7 Part C The Skeleton

Transcription

1 Chapter 7 Part C The Skeleton Part 2 The Appendicular Skeleton Consists of bones of the limbs and their girdles Pectoral girdle Attaches upper limbs to body trunk Pelvic girdle Attaches lower limbs to body trunk 7.4 The Pectoral Girdle Pectoral girdle (shoulder girdle) consists of clavicles (anteriorly) and scapulae (posteriorly) Attach upper limbs to axial skeleton Provide attachment sites for muscles that move upper limbs Offer great degree of mobility because: Scapulae are not attached to axial skeleton Socket of shoulder joint is shallow and does not restrict movement Clavicles Also called collarbones S-shaped sternal end articulates with sternum medially Flattened acromial end articulates laterally with scapula Anchor muscles and act as braces to hold the scapulae and arms out laterally Scapulae Also called shoulder blades; thin, triangular flat bones on dorsal surface of rib cage, between ribs 2 and 7 Each scapula has three borders Superior: shortest, sharpest border Medial (vertebral): runs parallel to spine Lateral (axillary): near armpit, ends superiorly in glenoid cavity fossa (shoulder joint) Scapulae (cont.) Each scapula has three angles where borders meet: Superior angle: between superior and medial Lateral angle: between superior and lateral Inferior angle: between medial and lateral 2016 Pearson Education, Inc. 1

2 Scapulae (cont.) Bone features Spine: prominent ridge posteriorly Acromion: lateral projection that articulates with acromial end of clavicle to form acromioclavicular joint Coracoid process: anterior projection that anchors bicep muscle of arm Suprascapular notch: opening for nerves Several large fossae named according to location 7.5 The Upper Limb 30 bones form skeletal framework of each upper limb Arm Humerus Forearm Radius and ulna Hand 8 carpal bones in the wrist 5 metacarpal bones in the palm 14 phalanges in the fingers Arm Humerus: only bone of the arm; the largest and longest bone of upper limb Articulates superiorly with glenoid cavity of scapula Articulates inferiorly with radius and ulna Arm (cont.) Bone features Head: proximal end that fits into glenoid cavity of scapula Anatomical neck: slight constriction inferior to head Greater tubercle is separated from lesser tubercle by the intertubercular sulcus Sites of attachment of rotator cuff muscles Surgical neck: most frequently fractured part of humerus Arm (cont.) Bone features (cont.) Deltoid tuberosity: about midway down shaft; site of deltoid muscle attachment Radial groove: carries radial nerve Trochlea: distal hourglass-shaped condyle Capitulum: distal ball-like condyle 2016 Pearson Education, Inc. 2

3 Medial and lateral epicondyles: points of muscle attachment Medial and lateral supracondyle ridges Fossae: coronoid, olecranon, and radial Forearm Two parallel bones form forearm skeleton: ulna and radius Proximal ends articulate with humerus and each other Distally articulate with each other at the radioulnar joint Interosseous membrane connects radius and ulna along their entire length Forearm (cont.) Ulna Medial bone in forearm Forms major portion of elbow joint with humerus Bone features Olecranon and coronoid processes: grip trochlea of humerus, forming hinge joint Processes separated by trochlear notch Radial notch: articulates with head of radius Ulnar head: knoblike distal portion Ulnar styloid process: ligament attachment Forearm (cont.) Radius Lateral bone in forearm Bone features Head: articulates with capitulum of humerus and radial notch of ulna Radial tuberosity: anchors biceps Ulnar notch: articulates with ulna Radial styloid process: anchors ligaments Clinical Homeostatic Imbalance 7.5 Colles fracture: break in distal end of radius Very common fracture because person falling attempts to break fall with outstretched hands Hand Bones of the hand include carpus, metacarpus, and phalanges Carpus (wrist): eight bones in two rows Proximal row: lateral to medial 2016 Pearson Education, Inc. 3

4 Scaphoid, lunate, triquetrum, and pisiform Distal row: lateral to medial Trapezium, trapezoid, capitate, and hamate Only scaphoid, lunate, and triquetrum form wrist joint Hand (cont.) Metacarpus (palm) Five metacarpal bones (I to V from thumb to little finger) form the palm Bases articulate with carpals, and heads articulate with proximal phalanges Phalanges (fingers) Fingers (digits): numbered I to V starting at thumb (pollex) Digit I (pollex) has two bones: no middle phalanx Digits II to V have three bones: distal, middle, and proximal phalanx Clinical Homeostatic Imbalance 7.4 Median nerve and tendons travel through carpal tunnel Tunnel formed by ligaments through wrist Carpal tunnel syndrome can occur from overuse and inflammation of tendons, which can compress median nerve, causing tingling and numbness 7.6 The Pelvic Girdle Also called hip girdle; is formed by 2 hip bones (coxal bones, or os coxae) and sacrum Attach lower limbs to axial skeleton with strong ligaments Transmit weight of upper body to lower limbs Support pelvic organs Less mobility but more stability than shoulder joint Three fused bones form coxal bone Ilium, ischium, and pubis Deep socket, acetabulum, formed at point of fusion receives head of femur Ilium Ilium Superior region of coxal bone Auricular surface articulates with sacrum (sacroiliac joint) Ischium Posteroinferior part of hip bone Pubis Anterior portion of hip bone Pubis joins at pubic symphysis joint 2016 Pearson Education, Inc. 4

5 Ilium (cont.) Superior region of hip bone Consists of body and winglike ala Iliac crests: thickened superior margin of ala Iliac crest ends at anterior superior iliac spine and posterior superior iliac spine Greater sciatic notch: sciatic nerve passage Gluteal surface contains three ridges: posterior, anterior, and inferior gluteal lines Iliac fossa: concavity on ala Auricular surface articulates with sacrum Arcuate line: defines pelvic brim Ischium Posteroinferior part of hip bone Consists of body and ramus Three important markings: Ischial spine Lesser sciatic notch Ischial tuberosity Pubis V-shaped anterior portion of hip bone Consists of the body and superior and inferior pubic rami Anterior border forms the pubic crest Lateral end forms pubic tubercle Obturator foramen: large opening formed by rami and body Pubic bones join at pubic symphysis Pubic arch (subpubic angle): formed by rami; main difference between male and female pelves Pelvic Structure and Childbearing Pelvis: formed by hip bones, sacrum, and coccyx Female pelvis tends to be wider, shallower, lighter, and rounder than male s Adapted for childbearing Pelvic brim (pelvic inlet): continuous oval ridge that runs from pubic crest through arcuate line and sacral promontory False pelvis: superior to pelvic brim True pelvis: inferior to pelvic brim; defines birth canal Pelvic outlet: inferior margin of true pelvis 2016 Pearson Education, Inc. 5

6 7.7 The Lower Limb Carries entire weight of erect body Subjected to exceptional forces during jumping or running Three segments of lower limb Thigh Leg Foot Thigh Femur is largest and strongest bone in the body, making up about one-fourth of person s height Articulates proximally with acetabulum of hip and distally with tibia and patella Patella: sesamoid bone in quadriceps tendon that protects knee joint Thigh (cont.) Bone features Fovea capitis: small pit in ball-like head Greater and lesser trochanters: muscle attachment sites Trochanters connected by intertrochanteric line and intertrochanteric crest Gluteal tuberosity blends into linea aspera, which diverges into medial and lateral supracondylar lines Thigh (cont.) Bone features (cont.) Distally, femur ends in lateral and medial condyles that articulate with tibia Medial and lateral epicondyles: sites of muscle attachment Adductor tubercle: medial epicondyle bump Patellar surface: articulates with patella Intercondylar fossa: lies between condyles Leg Made up of two parallel bones, tibia and fibula Connected by interosseous membrane Tibia: medial leg bone that receives weight of body from femur; transmits to foot Fibula Not weight bearing; no articulation with femur Several muscles originate from fibula 2016 Pearson Education, Inc. 6

7 Articulates proximally and distally with tibia Leg (cont.) Bone features Tibia Medial and lateral condyles Intercondylar eminence Tibial tuberosity Anterior border Medial malleolus Fibular notch Fibular: Head Lateral malleolus Clinical Homeostatic Imbalance 7.4 Pott s fracture occurs at distal end of fibula, the tibia, or both Common sports injury Foot Skeleton of foot includes bones of tarsus, metatarsus, and phalanges Tarsus: 7 tarsal bones form posterior half Body weight carried primarily by talus and calcaneus (heel) Calcaneal tuberosity: part that touches ground Sustentacular tali (talar shelf): supports talus Other tarsal bones: cuboid, navicular, and medial, intermediate, and lateral cuneiform bones Foot (cont.) Metatarsals Five metatarsal bones (I to V from hallux to little toe) Enlarged head of metatarsal I forms ball of the foot Phalanges 14 bones of toes Digit I (hallux, great toe) has two bones: no middle phalanx Digits II to V have three bones: distal, middle, and proximal phalanx Foot (cont.) Arches of the foot Maintained by interlocking foot bones, ligaments, and tendons 2016 Pearson Education, Inc. 7

8 Allow foot to bear weight Three arches Lateral longitudinal: low curve that elevates lateral part of foot Medial longitudinal: arch curves upwards Transverse: runs obliquely from one side of foot to other Clinical Homeostatic Imbalance 7.4 Fallen arches, also called flat feet, result from stress on tendons and ligaments of feet Can be caused by: Standing immobile for extended periods of time Running on hard surfaces without proper arch support Developmental Aspects of the Skeleton Infant skull has more bones than adult skull Skull bones such as mandible and frontal bones are unfused Skull bones connected by fontanelles Unossified remnants of fibrous membranes Ease birth and allow brain growth Four fontanelles Anterior, posterior, mastoid, and sphenoidal Clinical Homeostatic Imbalance 7.4 Congenital abnormalities may distort skull Cleft palate is the most common condition No medial fusion of right and left halves of palate Interferes with sucking Can lead to aspiration of food into lungs, which may result in aspiration pneumonia Developmental Aspects of the Skeleton (cont.) At birth, cranium is huge relative to face At 9 months, cranium is half the adult size Mandible and maxilla are foreshortened but lengthen with age Arms and legs grow at faster rate than head and trunk, leading to adult proportions Developmental Aspects of the Skeleton (cont.) Primary curvatures of thorax and sacrum are convex at birth, resulting in C- shaped spine 2016 Pearson Education, Inc. 8

9 Secondary curvatures of cervical and lumbar regions convex anteriorly as child develops Developmental Aspects of the Skeleton (cont.) As we age, intervertebral discs become thin, less hydrated, and less elastic Risk of disc herniation increases Several centimeters of height loss is common by age 55 Costal cartilages ossify Rigid thorax causes shallow breathing and less efficient gas exchange All bones lose mass, so fracture risk increases Clinical Homeostatic Imbalance 7.10 Appendicular skeleton can suffer from congenital abnormalities Hip dysplasia occurs in a little over 1% of infants Acetabulum forms incompletely or ligaments are loose, allowing head of femur to slip out of socket Treatments include splints or harness to hold femur in place or surgery to tighten ligaments 2016 Pearson Education, Inc. 9