Appendicular SKeleton

The Appendicular Skeleton

Fig. 5.8, p. 146

• 126 bones of the limbs (appendages), the pectoral girdle, and the pelvic girdle
• Girdles attach the limbs to the axial skeleton

The Shoulder (Pectoral) Girdle-Clavicle (Fig. 5.23(a-b), p.159

• The collarbone
• Holds the arm away from the upper thorax and helps prevent shoulder dislocation
• When the clavicle is broken, the shoulder region caves in medially
• Attaches medially at the manubrium (at the sternal end) and laterally at the scapula (helping to form the shoulder joint)
• Shoulder blades
• Triangular; “wings” because they flare out when we move arms posteriorly
• Flattened body with 2 important processes:
• Acromion : enlarged end of the spine of the scapula; connects with the clavicle laterally at the acromioclavicular joint
• Coracoid process: break-like; points over the top of the shoulder and anchors some of the muscles of the arm

Other Important Markings of the Scapula

Fig. 5.23 (c-d), p.159

• Suprascapular notch: just medial to coracoid process; nerve passageway
• Not directly connected to axial skeleton— held in place by trunk muscles
• 3 borders: superior, medial (vertebral), and lateral (axillary)
• 3 angles: superior, medial, and inferior
• Glenoid cavity: in the lateral angle; shallow socket that receives the head of the arm bone.

Shoulder Girdle:

Allows Wide Range of Motion

• Very light
• Attaches to axial skeleton at only one point– the sternoclavicular joint
• Loose attachment of the scapula allows it to slide back and forth against the thorax as muscles move
• Glenoid cavity is shallow and poorly reinforced by ligaments
• PROBLEM: easily dislocated

Arm: Humerus (long bone) (I)

Fig. 5.24 (a-b), p.160

• Proximal end: rounded head that fits into shallow glenoid cavity
• Anatomical neck: immediately inferior to proximal head; slight constriction
• Greater & lesser tubercles: anterolateral to head; sites of muscle attachment
• Separated by the intertubercular sulcus
• Surgical neck: just distal to tubercles; most frequently fractured area of the humerus

Arm: Humerus (long bone) (II)

Fig.5.24 (a-b), p.160

• Deltoid tuberosity: roughed area on the midpoint of shaft;l deltoid attaches
• Radial groove: runs obliquely down posterior of shaft; radial nerve fits here
• Trochlea: spool-like at the medial-distal end; articulates with bones of the forearm
• Capitulum: ball-like at the lateral-distal end; articulated with bones of the forearm
• Coronoid (anterior) & Olecranon (posterior) Fossa: above trochlea: allow processes of the ulna to move freely
• Flanked by medial & lateral epicondyles

Forearm: Radius (I)

Figure. 5.24(c), p. 160

• Lateral bone
• When the palm faces backward, the distal end of the radius becomes medial to the ulna
• Articulates proximally and distally with the ulna at the radioulnar joints
• Connected along the length with the ulna with flexible interosseous membrane
• Styloid process at the distal end

Forearm: Radius (II)

Fig. 5.24(c), p.160

• Disc-shaped head forms joint with the capitulum of the humerus
• Radial tuberosity: just below the head; bicep muscle attaches

Forearm: Ulna

Fig. 5.24(c), p.160

• Medial bone
• Coronoid process (anterior) & olecranon(posterior): at the proximal end; grip the trochlea of the numerous ina pliers-like grip
• These two processes are separated by the trochlear notch

Hand

Fig. 5.25, p.161q

• Eight carpal bones (2 irregular rows of 4 bones each); form the carpus (wrist)
• Movement among them is restricted by ligaments
• Metcarpals: palm
• Numbered 1 to 5 (thumb is 1, pinky is 5)
• In a fist, the heads become the knuckles
• Phalanges: fingers
• 3 bones in each finger (proximal, middle, distal); only 2 in thumb (proximal, distal)

Pelvic Girdle

Fig. 5.26, p.162

• Formed by 2 coxal bones (a.k.a ossa coxae or the hip bones) and the sacrum
• The pelvic girdle + the coccyx= the bony pelvis

Basics of the pelvic girdle

• Bones are large and heavy; securely attached to axial skeleton by the sacral attachment to the lowest lumbar vertebra
• Thigh bones securely attached to the girdle by deep sockets and reinforced by ligament
• Most important job: bears weight of upper body
• Reproductive organs, urinary bladder, and large intestine lie within pelvis

Hip Bones: Fusion of 3 Bones Ilium (Fig. 5.26, p. 162)

• Ilium: large & flaring; connected posteriorly to the sacrum at the sacroiliac joint
• Alae: wing-like portion (when you rest your hands on your hips)
• Iliac crest: upper edge of an ala; important landmark for intermuscular injections
• Anterior superior iliac spine: anterior end
• Posterior superior iliac spine: posterior end
• Small inferior spines below

Hip Bones: Fusion of 3 Bones

Ischium (Fig. 5.26, p. 162)

• Ischium: forms most inferior part of coxal bone; “sit down bone”
• Ischial tuberosity: roughened area that receives body weight when sitting
• Ischial spine: superior to tuberosity; important landmark (narrows outlet through pelvis through which the baby passes)
• Greater sciatic notch: allows blood vessels and sciatic nerve to pass posteriorly to thigh (buttock injections should be far from this area!!!)

Hip Bones: Fusion of 3 Bones

Pubis (Fig. 5.26, p.162)

• Pubis: most anterior portion of coxal bone
• Obturator foramen: allows blood vessels and nerves to pass to the anterior part of thigh
• A bone of bar from the rami of the pubis anteriorly & ischium posteriorly surrounds this
• Pubic symphysis: fusion of both pubic bones, forming this cartilaginous joint

Hip Bones: Fusion of 3 Bones

Acetabulum (Fig. 5.26, p.162)

• Deep socket that is the fusion of the ilium, ischium, and pubis
• Receives the head of the thigh bone (femur)

Two Pelvic Regions

Fig. 5.26, p. 162

• False pelvis: superior to true pelvis; medial to flaring ilia
• True pelvis: inferior to flaring ilia; surrounded by bone
• For women, the true pelvis MUST be large enough for the baby’s head to pass through
• The dimensions of the outlet (inferior) and inlet (superior) must be carefully measured

Chracteristics of the FEMALE

pelvis (Fig. 5.26 (c), p.162)

• Inlet is larger & more circular
• Shallower, and the bones are lighter and thinner
• Ilia flare more laterally
• Sacrum is shorter & less curved
• Ischial spines are shorter and father apart (creating larger outlet)
• Pubic arch is more rounded (the pubic arch is greater)

Foot

Fig. 5.28, p.165

• Two functions: supports body weight and acts as a lever to propel our bodies as we walk or run
• Tarsus: posterior of foot; 7 tarsal bones
• 2 largest carry most of the body weight: the calcaneus (heelbone) and talus (lied between the tibia and calcaneus)
• Metatarsals: sole of the foot; 5 bones
• Phalanges: toes; 14 bones
• All toes have 3 bones, except the big toe (2 bones)

Arches of the Foot

Fig. 5.29, p.165

• Bones are arranged to form 3 arches
• 2 arches are longitudinal (one medial and one lateral), and 2 arch is transverse
• The ligaments and tendons in the foot help secure the foot bones, but allow a certain amount of give or springiness
• Weak arches are referred to as “fallen arches” or “flat feet”

Joints

P.165-173

Joints (Articulations)

• Sites where 2 or more bones meet
• Hyoid bone-only unarticulated bone in body
• Two functions:
• Hold bones in place
• Give rigid skeleton mobility
• Two ways joints are classified:
• Functionally
• Structurally

Funtional Classifications of Joints

• Synarthroses: immovable
• Mostly restricted to axial skeleton
• Amphiarthroses: slightly movable
• Mostly restricted to axial skeleton
• Diarthroses: freely movable
• Predominate in the limbs

Structural Classification of Joints

Fig. 5.30, p.168 & Table 5.3, p.169

• Fibrious: fibrous tissue connects bones
• Generally immovable (synarthroses)
• Cartilaginous: cartilage connects bones
• Generally slightly movable (amphiarthroses)
• Synovial: joint cavity connects bones
• Generally freely movable (diarthroses)

Fibrous Joints

• United by fibrous tissue
• Eg. Sutures in the skull (Fig. 5.30(a), p.168)
• Irregular edges interlock and are bound by connective tissue fibers
• Syndesmoses- fibers connecting bones are longer than in sutures; more “give” to the joint
• Eg. Joint connecting the distal end of the tibia and fibula

Cartilaginous Joints

• Bone ends are connected by fibrocartilage
• Eg. of the slightly movable (amphiarthrotic) joints: pubis symphysis and intervertebral joints (Fif. 5.30 (e-d), p.168)
• Syndchondroses: immovable cartilaginous joints (synarthrotic)
• Eg. Epiphyseal plates and joints between first ribs & sternum (Fig. 5.30 (c), p.168)

Synovial Joints

Fig. 5.30 (f-h), p. 168

• Bones articulate at a joint cavity filled with synovial fluid; eg. Limbs
• 4 characteristics:
• Articular (hyaline) cartilage covers bone ends
• Joint surfaces enclosed by sleeves of fibrous c.t. (articular capsule), lined with a smooth synovial membrane
• Articular capsule encloses joint vanity, which contains lubricating synovial fluid
• Fibrous layer of capsule reinforced by ligaments

Bursae & Tendon Sheaths

• Bags of lubricant closely associated with synovial joints (Fig. 5.32, p. 170)
• Act like ball bearings to reduce friction
• Bursae: flattened fibrous sacs lined with synovial membranes and containing a thin film of synovial fluid
• Common where ligaments, muscles, skin, tendons, or bones rub together
• Tendon sheaths: an elongated bursa; wrapped around a tendon subject to friction

Homeostatic Imbalance:

Dislocation

• The bone is forced out of its normal position in the joint cavity
• Reduction: process of returning the bone to its proper position
• Should ALWAYS be done by a physician!!!

Homeostatic Imbalance

Bursitis&Sprain

• Bursitis: “water on the knee”
• Inflammation of bursae or synovial membranes in the patellar area
• Sprain: Inflammation (or possible tearing) of the ligaments or tendons
• Causes swelling
• Slow to heal because tendons and ligaments are poorly vascularized

Homeostatic Imbalance:

Arthritis

• Describe over 100 inflammatory or degenerative diseases that affect the joints
• Most widespread crippling disease in the U>|S
• All forms start with: pain, stiffness, & swelling of the joints
• Different types of arthritis have different long-lasting effects
• Acute forms: bacterial infections; treat with antibiotics
• Synovial membrane thicken and fluid decreases=increased friction=PAIN

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