Chapter 8: The Appendicular Skeleton

BIO 210 Lab Instructor: Dr. Rebecca Clarke

Appendicular Skeleton

  Allows us to move and manipulate objects Includes all bones besides axial skeleton:  the limbs  the supportive girdles   Pectoral (shoulder) Pelvic

Appendicular Skeleton

Figure 8–1

Pectoral Girdle

     Also called the shoulder girdle Positions shoulder joints Connects the arms to the body Provides base for muscle attachment Helps move upper limbs

Pectoral Girdle

Figure 8–2a

Pectoral Girdle

  Consists of:   2 clavicles 2 scapulae Connects with axial skeleton only at the manubrium (clavicle articulations)

Clavicle

     Also called collarbone Long, S-shaped bone Originates at manubrium (sternal end) Articulates with scapula (acromial end) Relatively fragile so fractures common

Clavicle

  Sternal End:   Square, flat surface Articulates with manubrium; only ones between axial skeleton and pectoral girdle Acromial End:   Flatter, broader end Articulates with acromion of scapula Figure 8–2b, c

Scapula

    Also called shoulder blade Broad, flat triangle Articulates with arm and collarbone Skeletal muscles support/position   Extreme mobility  Not much strength

Scapula: Posterior Surface

 Body   Broad, flat, triangular area Has 3 borders/ margins    Superior Medial Lateral Figure 8–3c

Scapula: Posterior Surface

 Spine  Large ridge across posterior surface  Shoulder blade  Supraspinous fossa  Depression superior to spine  Infraspinous fossa  Depression inferior to spine Figure 8–3c

Scapula: Posterior Surface

 Acromion   Large, posterior extension at lateral end of spine Articulates with clavicle (acromial end) Figure 8–3c

Scapula: Lateral View

 Glenoid fossa (cavity)    Cup-shaped, lateral depression Articulates with humerus Forms shoulder joint Figure 8–3c

Scapula: Lateral View

 Coracoid process   Smaller, anterior projection superior to glenoid cavity Near clavicle vs coronoid process on mandible near nose) Figure 8–3c

Scapula: Anterior Surface

 Subscapular fossa  Depression on smooth, anterior side of body Figure 8–3a

Bones of the Upper Limbs

     Brachium (arm) Antebrachium (forearm)  Ulna  Radius Carpals (wrist) Metacarpals (hand) Phalanges (fingers)

Humerus

   Only bone in brachium (arm) Extends from scapula to elbow Articulates with pectoral girdle  on proximal end (head) – with glenoid fossa of scapula  on distal end – with radius and ulna (bones of antebrachium)

Humerus

    Head  Large, ball-shaped structure on proximal end Greater tubercle  Larger, rounded projection on lateral/posterior surface of epiphysis Lesser tubercle  Smaller projection on medial/anterior surface Intertubercular groove  Separates tubercles Figure 8–4

Humerus

   Anatomical neck  Narrow groove between base of head and tubercles  Margin of joint capsule Surgical neck  At metaphysis  Where fractures often occur Deltoid tuberosity  Rough ridge on-anterior surface of shaft  Where deltoid muscle attaches Figure 8–4

Humerus

 Condyle   = rounded projection for muscle attachment Distal epiphysis where humerus articulates with radius and ulna  “Knuckles” on anterior surface of humerus Figure 8–4

Humerus

    Lateral epicondyle Medial epicondyle  More prominent than lateral one Trochlea (“pulley” or “spool”)   In center of condyle (middle “knuckle) Where trochlear notch of ulna rotates during forearm flexion Capitulum  Forms a “cap” over the radius Figure 8–4

Humerus

  Coronoid fossa  On anterior surface  Articulates with coronoid process of ulna Olecranon fossa   On posterior surface Articulates with olecranon of ulna Figure 8–4

Antebrachium (Forearm)

 Consists of 2 long bones:   Ulna (medial) Radius (lateral)   “Rotates” Site of radial pulse Figure 8–5

Ulna

 Olecranon (process)  Large, curved projection (like cobra head) on proximal end     “U” for ulna Articulates in olecranon fossa of humerus Superior lip of trochlear notch Point of elbow Figure 8–5

Ulna

  Trochlear notch   Anterior curved surface of proximal epiphysis Articulates with trochlea of humerus Coronoid process   Inferior lip of trochlear notch Articulates in coronoid fossa of humerus Figure 8–5

Ulna

  Head   Much smaller, distal epiphysis (near wrist) Articulates with radium and carpal (wrist) bones Styloid process   Medial pointed extension at distal epiphysis On posterior, lateral surface of head Figure 8–5

Ulna: Articulations with the Humerus   Forearm extended:  Olecranon enters olecranon fossa Forearm flexed:  Coronoid process enters coronoid fossa

Radius

   Head   Disc-shaped proximal epiphysis Articulates with humerus Neck  Narrow region between head and tuberosity Radial tuberosity   Structure at proximal end of diaphysis below neck Marks attachment site of biceps brachii muscle Figure 8–5

Radius

  Shaft  Curves and broadens  Distal portion much larger than distal portion of ulna Styloid process  Lateral pointed extension at distal epiphysis  Stabilizes wrist joint Figure 8–5

Carpal Bones

 Allow wrist to bend and twist  8 bones  “Sam likes to push the toy car hard.”

Carpal Bones

 Scaphoid  Lunate  Triquetrum  Pisiform  Trapezium  Trapezoid  Capitate  Hamate

Wrist and Hand Bones

Figure 8–6

Metacarpal Bones

   5 long bones of the hand Numbered I–V from lateral (thumb) to medial Articulate with proximal phalanges

Phalanges (Phalanx=singular)

 Finger bones   I (lateral)   Pollex (thumb): 2 phalanges (proximal, distal) II -V  3 phalanges (proximal, medial or middle, distal)

Pelvic Girdle

   Functions   Weight-bearing Locomotion Bones more massive than those of pectoral girdle Strong to bear body weight

Pelvic Girdle

  Made up of 2 hip bones (coxal bones or pelvic bones) Each hip bone is made up of 3 fused bones:  Ilium (articulates with sacrum)   Ischium Pubis

Pelvic Girdle

Figure 8–7

Pelvic Girdle: Ilium

    Largest hip bone Superior part of coxae Fused to ischium (posteriorly) and pubis (anteriorly) Articulates with sacrum – attaches pelvic girdle to axial skeleton Figure 8–7

Pelvic Girdle: Ilium

     Iliac crest  Superior border Anterior superior iliac spine (ASIS) Anterior inferior iliac spine (AIIS) Posterior superior iliac spine (PSIS) Posterior inferior iliac spine (PIIS) Figure 8–7

Pelvic Girdle: Ilium

   Iliac fossa  Depression on anterior aspect Sacroiliac joint  Between posterior superior and inferior spines; where ilium and sacrum articulate Greater sciatic notch   Inferior to PIIS Passageway for large sciatic nerve Figure 8–7

Pelvic Girdle: Ischium

    Posterior-inferior part of coxae Ischial spine  Inferior to greater sciatic notch  At posterior-superior end Lesser sciatic notch  Inferior to ischial spine Ischial tuberosity  Thickened posterior-inferior part  Bears body weight when seated (“sit bone”) Figure 8–7

Pelvic Girdle: Pubis

  Anterior-inferior part of coxae Pubic symphysis  Joint where anterior medial surfaces of pubic bones are interconnect by fibrocartilage pad  Limits movement between pubic bones of left and right hipbones Figure 8–7

Pelvic Girdle: Acetabulum

    Also called the hip socket Large, concave socket on lateral surface of os coxae Meeting point of ilium, ischium, and pubis Articulates with head of femur Figure 8–7

Pelvic Girdle: Obturator Foramen    Large space encircled by pubis and ischium Closed by sheet of collagen fibers Provides base for hip muscles Figure 8–7

Pelvis

  Consists of:    2 hip bones Sacrum Coccyx (of axial skeleton) Stabilized by ligaments of pelvic girdle, sacrum, and lumbar vertebrae

Pelvis

Figure 8–8

Pelvic Openings

  Pelvic inlet – (anterior) space enclosed by pelvic brim Pelvic outlet – opening bounded by coccyx and ischial tuberosities Figure 8–9

Pubic Angle

 Inferior angle between pubic bones Figure 8–10

Bones of the Lower Limbs

      Femur (thigh) Patella (kneecap) Tibia and fibula (leg) Tarsals (ankle) Metatarsals (foot) Phalanges (toes)

Femur

   Longest, heaviest bone Transfers body weight to ground Articulates with:   coxae at acetabulum tibia at knee joint Figure 8–11

Femur

  Head  Large, round proximal end  Articulates at acetabulum Neck   Narrow connector between head and shaft Joins shaft at angle Figure 8–11

Femur

  Greater trochanter  Large process at superior end of shaft Lesser trochanter  Smaller process inferior to neck on medial /posterior side Figure 8–11

Femur

  Lateral condyle  Large, rounded, lateral projection at distal epiphysis  Articulates with lateral condyle of tibia Medial condyle  Large, rounded, medial projection at distal epiphysis  Articulates with medial condyle of tibia Figure 8–11

Femur

 Intercondylar fossa  Depression between condyles on posterior side Figure 8–11

Femur

 Patellar surface  Flattened area between condyles on anterior side Figure 8–11

Patella

  Large sesamoid bone Forms within tendon of quadriceps femoris (extends/straightens the knee) Figure 8–12

Tibia

 Larger, medial bone; supports body weight  Also called the shinbone Figure 8–13

Tibia

  Lateral condyle   Lateral projection at proximal epiphysis Articulates with lateral condyle of femur Medial condyle   Medial projection at proximal epiphysis Articulates with medial condyle of femur Figure 8–13

Tibia

 Tibial tuberosity    Roughened area on anterior surface Inferior to condyles Attachment for patellar ligament Figure 8–13

Tibia

  Anterior margin  Ridge that begins at tibial tuberosity and extends distally along anterior surface (“shin bone”) Medial malleolus (“little mallet”)  Projection on medial side at distal epiphysis Figure 8–13

Fibula

 Slender, lateral bone of lower leg Figure 8–13

Fibula

  Head  Articulates with proximal tibia Lateral malleolus  Projection on lateral side at distal epiphysis   Articulates with distal tibia Provides lateral stability to ankle Figure 8–13

Tarsal Bones

 Allow ankle to bend and twist  7 bones

Ankle and Foot Bones

Figure 8–14a

Tarsal Bones

    Talus Calcaneous Navicular Cuboid  Cuneiforms (3) Note: movement more restricted than wrist/hand

Metatarsal Bones

   5 long bones of the foot Numbered I–V from medial (big toe) to lateral Articulate with proximal phalanges

Phalanges

 Toe bones   I (lateral)   Hallus (big toe): 2 phalanges (proximal, distal) II -V  3 phalanges (proximal, medial or middle, distal)