Lab Exam #2 Notes PDF

# Exercise #12 ## The Appendicular Skeleton It is composed of 126 bones that make up the appendages and the pelvic and pectoral girdles. ## Pectoral Girdle (2 paired bones) The Pectoral girdle consists of the anterior Clavicle and posterior Scapula. The clavicle has two ends: Acromial (lateral), St...

# Exercise #12 ## The Appendicular Skeleton It is composed of 126 bones that make up the appendages and the pelvic and pectoral girdles. ## Pectoral Girdle (2 paired bones) The Pectoral girdle consists of the anterior Clavicle and posterior Scapula. The clavicle has two ends: Acromial (lateral), Sternal (medial). The Clavicle can be differentiated between left and right by looking at the Conoid tubercle found posteriorly at the acromial end of the clavicle. When properly oriented the conoid tubercle will always point downward and posteriorly. The clavicle acts as a strut. The Scapula is the wings of the human being. Each has two large processes, the Acromion an enlarged process found on the posterior surface, and lateral. The clavicle articulates with the acromion. The Coracoid process is a smaller beak-like process which is found anteriorly, at the base of which is found the Suprascapular notch, which allows nerves and blood vessels to pass. Also found in the scapula laterally is the Glenoid cavity a shallow socket which holds the humerus. The shoulder girdle is very light and allows for great mobility for three reasons: 1. The Sternoclavicular joint is the only attachment to the axial skeleton. 2. Loose attachments of the scapula allow sliding due to muscular activity against the thorax. 3. The shallow glenoid cavity gives little stability for the shoulder joint. All the flexibility leads to easy dislocation. ## The Arm The arm is composed of three bones, the Humerus (upperarm), and the Ulna and Radius (lower arm or forearm). ### Humerus The humerus is a long bone. At the rounded head or epiphysis is found laterally the Greater tubercle, and anteriorly the Lesser tubercle. Midshaft, the Deltiod tuberosity is found laterally, this is the attachment site of the deltiod muscle. At the other end of the humerus there are 2 condyles, the Medial Trochlea (the spool) which articulates with the ulna, and the lateral Capitulum which articulates with the radius. These are flanked by Medial and Lateral epicondyles, the medial epicondyle has the ulnar nerve running in a groove beneath it, this is also called the funny bone. Anteriorly the medial Coroniod fossa and laterally the Radial fossa and posteriorly the Olecranon fossa allow room for the ulna and radius processes to move freely when the elbow is flexed and extended. ## The Antebrachium (the forearm) In the anatomical position the Radius is Lateral and the Ulna is medial. The Radius has an anterior radial tuberosity that is the point of attachment of the tendon of the biceps muscle. The radius also has a lateral Styloid process at the distal head (lateral). The Ulna has a Coronoid process anterior and lateral and the Olecranon process which is posterior and medial, these are separated by the Trochlear notch these articulate with the humerus. The radial notch articulates with the head of the radius. The ulnar Styloid process is an attachment point of the ligament of the wrist. ## The Hand or Manus Three groups of bones: 1. Carpus (wrist bones). 2. Metacarpals (bones of the palm). 3. Phalanges (bones of the fingers). ### Carpal bones There are eight carpal bones, two irregular rows of four bones. Closest to the palm and on the pinky side or medial side are the Hamate, the Capitate, the Trapezoid and the Trapezium. Beneath these and articulating with the ulna and radius are medial to lateral the Pisiform, which is on top of the Triquetral/ Triquetrum, the Lunate and the Scaphoid. All of these are bound together by ligaments. ### The Metacarpals These bones are numbered simply 1-5 from the thumb, #1, to the pinky #5. Heads articulate with the phalanges to become knuckles when the hand is in a fist. ### The Phalanges These bones are numbered in the same way 1-5, the thumb (pollux) #1 and have distal middle and proximal parts, except for the thumb which has only distal and proximal parts. ## Pelvic Girdle The pelvic girdle consists of 2 Coxal bones, the Ossa coxae, and the Sacrum and the Coccyx (usually included in the axial skeleton). The bones are heavy and massive, and attach securely to the axial skeleton. Main function is weight bearing. Sockets for the femur are deep. Each coxal bone is a fusion of three bones: 1. The Illium. 2. The Ischium. 3. The Pubis. ### The Ilium The largest of the pelvic bones, connected to the sacrum, comprises the superior/posterior portion of the pelvis. The Ala are two broad planes found medially. The Iliac crests are the superior margins of the Iliac bone (felt when you put your hands on your hips). The Lesser and Greater Sciatic Notches allow blood vessels and nerves to pass to and from the thigh. ### The Ischium The ischium comprises the inferior and posterior portion of the coxal bones. The Ischial tuberosity bears the weight of the body while sitting. ### The Pubic bone The Pubic bones are the most anterior part of the pelvis. The Pubic ramus and the Ramus of the Ischium form the bones that enclose the Obturator foramen, which allows blood vessels and nerves to pass. The pubic crest is found where the two pubic bones meet. It is anterior and forms the anterior/superior part of the pelvis. This also forms the pubic arch underneath. The Pubic crest links both parts of the pubic bone at the Pubic Symphysis (a fibrocartilage pad). The Ilium, ischium and the pubic bones fuse into a deep socket, the Acetabulum which receives the femur. #### Comparison of the Male and Female pelvis. Female pelvis is modified for child bearing and is wider, shallower lighter and rounder. The False pelvis is superior to the Arcuate line and supports the abdominal viscera. The True pelvis is inferior to the arcuate line. The Pelvic inlet or Pelvic brim is the opening from the Sacral Promontory and the arcuate lines. The female's is oval/wide, and the male is heart-shaped. The pelvic outlet is the inferior margin of the true pelvis. The female coccyx is projected more posteriorly than the males. The Pubic Arch angle is larger in the female pelvis ## Thigh The Femur or thigh bone is the heaviest and strongest bone in the body. Ball-like head articulates with the acetabulum. Small pit in the head is called the Fovea capitis, allows the entrance of a small ligament. The Neck is the weakest point and is usually broken when the leg is damaged. The Greater and Lesser trochanters lie between the neck and the shaft, with the Intertrochanteric crest inbetween. The Gluteal tuberosity is posterior and the Linea aspera runs below the tuberosity. Both are sites of muscle attachment. The Lateral and Medial condyles articulate with the tibia. The medial Adductor tubercle is a bump where the large Adductor magnus muscle attaches. The Patella is a triangular sesamoid bone enclosed in the Quadricep tendon. The patella guards the knee joint. ## The Lower leg Consists of two bones the Fibula and the Tibia (the shin bone), which is larger and medial, has Medial and Lateral condyles which receive the distal ends of the femur. The Tibial tuberosity is the site of patellar ligament attachment. The Medial Malleous, which is distal, forms the medial part of the ankle. The Anterior crest/border is right below the skin, and inferior to the tuberosity. ### The Fibula The Fibula is a thin stick-like bone with a sharp anterior crest that terminates in a Lateral malleous, the outer ankle bulge. ## The Foot Three groups of bones: 1. Tarsals. 2. Metatarsals. 3. Phalanges. There are seven Tarsal bones, 5 Metatarsals, and 14 Phalanges. ### Tarsal bones The Calcaneous (the heel bone), lies beneath the Talus which bears the bodies weight, the Navicular is medial and the Cuboid is lateral, these are followed closest to the Metatarsals by the Medial, Intermediate and the Lateral Cuneiforms. ### Metatarsals The Metatarsals are numbered 1-5 from the big toe to the pinky toe. ### Phalanges The phalanges are numbered1-5 from the big toe to the pinky toe and have distal, middle and proximal parts, except for the big toe which only has distal and proximal parts. The bones of the foot are arranged into three arches, 2 Longitudinal (medial and lateral) and one Transverse arch. Ligaments hold the boned in place and foot muscle tendons hold arches together. Weakened arches are called Fallen arches or Flat feet.