Lesson 2 Chapter 7 – The Skeletal System

LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 1 Unit 3 Study Guide Appendicular Division: The appendicular skeleton includes the bones of the upper extremities (arms, forearms, and hands), the pectoral (shoulder) girdle, the pelvic (hip) girdle, and the bones of the lower extremities (thigh, knee, leg, and foot). Its components are outside the body main axis. The bones of the upper extremities are the humerus, ulna, radius, carpals (wrist bones), metacarpals (hand bones), and phalanges (finger bones). The humerus in the arm articulates with the scapula at the shoulder joint and with the ulna and radius at the elbow. The radius and ulna in the forearm articulate with the carpals at the wrist. The ulna articulates with the humerus and forms the elbow. The carpals are small, flat, irregularly shaped wrist bones. They articulate with the metacarpals in the hand. The metacarpals articulate with the phalanges. In the pelvic girdle are two hip bones. Each coxa (hip bone) forms from fused bones. The two coxae, sacrum, and coccyx form the pelvis, a bowl-shaped cavity that supports and protects many abdominal organs. The three fused bones of each coxa are the ilium, ischium, and pubis. LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 2 Bones hang suspended from bony girdles anchored to the axial skeleton. Appended to the longitudinal axis of the body Pectoral girdle attach the upper limbs. Pelvic girdle attach the lower limbs. Each 1imb is composed of 3 major segments connected together by freely movable joints. Appendicular skeleton functions in movement and manipulation. Pectoral Girdle consists of two bones: clavicle (anterior side), scapula (posterior side). 2 girdles plus their muscles form the shoulders. Anteriorly the medial end of each clavicle joins the sternum -- the distal ends meet the scapulae laterally. Pectoral girdles provide insertion points for many muscles. Girdles are very light and allow the upper limb a high degree of flexibility and mobility. Only attachment point of the pectoral girdles to the axial skeleton is at the sternoclavicular joints anteriorly. The socket of the shoulder joint is small and shallow and poorly reinforced by ligaments. Good for flexibility but poor for stability. Appendicular Division: Clavicle Medial end is attached to the sternum Lateral end is attached to the acromial process Clavicles: Collar bones. Slender, doubly curved long bones. Extend horizontally across the upper thorax. Clavicles act as braces anteriorly. They hold out the scapulae and their limbs away from the upper, narrower portion of the thorax. Exceptionally sensitive to muscle pull and become noticeably larger and stronger in those performing manual labor. LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] Appendicular Division: Scapula 2 surfaces - Subscapular fossa is the anterior scapula*** - Supraspinous fossa is the posterior scapula 3 borders 3 angles Scapulae: Shoulder blades. Flattened triangular bones. 3 borders: superior border - shortest & sharpest border, Vertebral border - parallels vertebral column, Lateral border - abuts with armpit. Has shallow fossa (glenoid cavity) articulates with humerus of arm. The lateral aspect of the scapulae ends in the anterior projection - acromion - which articulates with the clavicle forming the acromioclavicular joint which is crucial in attaching the upper limb to the body. Acromion: the lateral extension of the spine of the scapula, forming the highest point of the shoulder. Glenoid cavity: the concavity in the head of the scapula that receives the head of the humerus to form the shoulder joint Spine: the posterior back end and separates the supra- from the infraspinatous fossa. 3 LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] Pelvic Girdle Hip girdle. Attaches the lower limbs to the axial skeleton. Transmits upper body weight to the lower limbs. Secured to the axial skeleton by some of the strongest ligaments in the body. Sockets are deep and cuplike and heavily reinforced by ligaments. Formed by a pair of coxal bones (ossa coxae) - hip bones. Each coaxal bone unites with its partner anteriorly and with the sacrum posteriorly. Deep basin structure formed - bony pelvis. Each large coaxal bone consist of 3 separate bones: ilium, ischium, pubis. Fused in adults forming a deep socket - acetabulum -which articulates with the head of the femur. Appendicular Division: Pelvic Bone Comprise of two hip bones joined at the pubic symphysis anteriorly and to the sacrum posteriorly. 4 LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 5 Appendicular Division: Upper Extremity (Upper Limb) General: 30 separate bones. Comprises the arm, forearm and the hand. Arm: Part of the upper limb between the shoulder and elbow. Humerus - sole bone. Typical long bone. Articulates with the scapula at the shoulder & radius & ulna at elbow. Proximal end (head) fits into the glenoid cavity. Distal end has 2 condyles that articulate with the ulna arid radius respectively. Forearm: Radius and ulna - 2 parallel bones. Proximally they articulate with the humerus. Distal end forms the joints with the bones of the wrist. Both articulate with each other at small radioulner joints. Connected lengthwise by an interosseous membrane. Ulna: Slightly longer. Forms the elbow joint with the humerus. Shaft is triangular and ridged. Proximal end articulates with the humerus. Distal ulnar head is separated from the bones of the wrist by a fibrocartilage disc. Pinky side. Radius: Triangular. Articulates with the humerus and ulna proximally. Distally it articulates with the carpal bones of the wrist. Major forearm bone contributing to the wrist joint. When the radius moves the hand moves with it. Thumb side. Hand: Carpus - wrist. Metacarpals - palm. Phalanges - fingers Proximal Region of the Humerus The proximal region of the humerus is the first part, articulating with the scapula to form the glenohumeral joint (shoulder joint). The important anatomical features of the proximal humerus are the head, anatomical neck, surgical neck, greater and lesser tubercles and intertubercular sulcus. A tubercle is a round nodule, and signifies an attachment site of a muscle or ligament. The head of the humerus projects medially and superiorly to articulate with the glenoid cavity of the scapula. The head is connected to the tubercles by the anatomical neck, which is short in width and nondescript. The greater tubercle is located laterally on the humerus. It has an anterior and posterior face. The greater tubercle serves as attachment site for 3 of the rotator cuff muscles (supraspinatus, LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] infraspinatus and teres minor). The lesser tubercle is much smaller, and more medially located on the bone. It only has an anterior face. It is a place of attachment for the last rotator cuff muscle – subscapularis. Separating the two tubercles is a deep depression, called the intertubercular sulcus, or groove. The tendon of the long head of biceps brachii runs through this groove. The edges of the intertubecular sulcus are known as lips. Tendons of the pectoralis major, teres major and latissimus dorsi attach to the lips of the intertubecular sulcus. 6 LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 7 LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 8 Appendicular Division: Lower Extremity (Lower limbs) Ilium: Large flaring bone forming the major portion of the coxal bone. Winglike portion is called the ala. Thickened superior margin of the ala - iliac crest. Ischium: Roughly L- or arc shaped. Upper thicker part attaches to the ilium. Lower thinner ramus joins the pubis. Pubis: Pubic bone. Forms the anterior portion of the os coxa. Opening formed by the pubic rami and the ischial rami is the obturator foremen. Bodies of the 2 pubic bones are joined by fibrocartilage disc forming the pubic symphysis. Thigh: Lower limbs carry entire weight of the erect body. Thicker and stronger bones. Bones specialized for stability and weight bearing. Femur is the single thigh bone. Largest, longest and strongest. Clothed by bulky muscles. Length is about 1/4 of persons height. Proximally articulates with the hip bone - acetabulum. Articulates with the knee. Head is carried on a short neck that angles laterally to join the shaft. Neck is the weakest part of the femur. Distally the femur articulates with the tibia. Smooth patellar surface between the condyles (anterior) articulates with the patella. Lower 2 parallel bones - tibia and fibula. Connected by interosseous membrane. Articulate with each other proximally and distally. Tibiofibular joints of the leg allows for essentially no movement. Bones are less flexible but stronger and more stable. Larger tibia articulates with the femur to form the hinge joint of the knee and distally with the talus bone of the foot. Tibia: Shinbone. Receives weight of the body from the femur and transmits it to the foot. Except for the femur, tibia is the largest and strongest bone. Broad proximal end articulate with the femur condyles. Fibula: Non-weight bearing bone. Sticklike with slightly expanded ends. Articulates proximally and distally with the tibia. Upper end is the head; lower end is the lateral malleolus -ankle bone. Foot: Tarsals, Metatarsals, Phalanges. 2 important functions: supports body weight, acts as a lever to propel the body forward. Body weight is carried primarily by the 2 largest posterior tarsals: talus - articulates with tibia and fibula and the calcaneus – heel. The enlarged part of the metatarsals (head) forms the ball of the foot. LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] Appendicular Division: Femur Also known as the thigh bone. Greater and lesser trochanter are bony protuberance on the inner side of the neck of the femur that acts as an attachment point for some of the muscles of the thigh and buttocks. Condyle: the rounded projection on the articulating end of a bone, such as the ball portion of a ball-and-socket - Lateral and medial Epicondyle: A rounded projection at the end of a bone, located on or above a condyle and usually serving as a place of attachment for ligaments and tendons. - Lateral and medial Condyle vs Epicondyle • Condyle appears more prominent than the epicondyle. • Condyles are usually more round shaped than epicondyles. • Condyle is smooth and large, whereas epicondyle is rough and small. • Condyle articulates with a bone, but epicondyle provides surface for muscle and ligament attachment. 9 LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 10 Tibia Tibia is a large and strong bone that connects ankle and knee by articulating with femur in the proximal region, forming a hinge joint, and by articulating with talus bone in the ankle at its distal end. Tibia is also known as shinbone, and it is the second largest and strongest bone in the body. The main role of the tibia is to transfer the bodyweight from femur to foot. The proximal end of tibia is broad and contains two concave condyles; lateral condyle and medial condyle that articulate with lateral and medial condyles of the femur at knee joint. Tibial tuberosity, the prominent process on the anterior surface, provides the point of attachment for the patellar ligament. Anterior crest of the tibia does not have a muscle cover. At the distal end of tibia, the medial surface forms medial malleolus, which articulates with talus bone of the ankle. The point of articulation with the fibula is the fibular notch. Fibula Fibula is a long sticklike bone, which is connected to tibia at both distal and proximal ends laterally. It does not serve to transfer the bodyweight, but provides sites for muscle attachments. An enlarged head is found at its proximal end where the lateral condyle of tibia articulates. At its distal end, a projection called lateral malleolus articulates with the talus. Lateral malleolus is responsible for providing stability to the ankle and its bones. Fibula is bound to the tibia at its medial border by an interoseus membrane. What is the difference between Tibia and Fibula? • Tibia is larger and stronger than fibula. • Fibula does not form the knee joint, whereas tibia does. • Tibia is a weight bearing bone, whereas fibula is nonweight bearing bone. • Proximal end of tibia articulates with femur, while that of fibula articulates with the tibia. • The thickness of the tibia is much greater than the fibula. LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] Appendicular Division: Patella (Knee Cap) A flat triangular bone located at the front of the knee joint. Protects the anterior articular surface of the knee joint. It is the largest sesamoid bone in the human body. 11 LESSON 2 Chapter 7 – The Skeletal System [Appendicular Division] 12 Acetabulum: the cup-shaped cavity on the lateral surface of the hip bone, receiving the head of the femur. Overall Iliac crest Hip bone MALE PELVIS FEMALE PELVIS Narrow, heavy and thick. Outlet and inlet narrower Pubic arch < 90 degrees Longer and more curved Acetabulum – large Obturator foramen – round Wide, light and thin Outlet and inlet wider Pubic arch > 90 degrees Shorter and less curved Acetabulum – small Obturator foramen - oval