Anatomy of Head & Neck (Lec. 6) PDF

Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Lower Limbs: The lower limb consists of four major parts: a Girdle formed by the (hip bones), Thigh (femur), Leg (tibia & fibula), and Foot (tarsal, metatarsal, and phalanges) Hip Bones: The left and righ...

Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Lower Limbs: The lower limb consists of four major parts: a Girdle formed by the (hip bones), Thigh (femur), Leg (tibia & fibula), and Foot (tarsal, metatarsal, and phalanges) Hip Bones: The left and right hip bones (innominate bones, pelvic bones) are two irregularly shaped bones that form part of the pelvic girdle, the bony structure that attaches the axial skeleton to the lower limbs. Composition of the Hip Bone The hip bone is composed of the three parts: the ilium, pubis and ischium. Prior to puberty, the triradiate cartilage separates these parts and fusion only begins at the age of 15-17 (Figure 6.1). Figure 6.1: The anatomical position of hip bones and its three parts. Together, the ilium, pubis and ischium form a cup-shaped socket known as the acetabulum. The head of the femur articulates with the acetabulum to form the hip joint. The Ilium The ilium is the widest and largest of the three parts of the hip bone, and is located superiorly. The body of the ilium forms the superior part of the acetabulum. 36 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Immediately above the acetabulum, the ilium expands to form the wing which has two surfaces: Inner surface: has a concave shape, which produces the iliac fossa (site of origin of the iliacus muscle), (Figure 6.2) External surface (gluteal surface): has a convex shape and provides attachments to the gluteal muscles. Figure 6.2: The bony landmarks of the ilium. The Pubis The pubis is the most anterior portion of the hip bone. It consists of a body, superior ramus and inferior ramus (ramus = branch). Pubic body: located medially, it articulates with the opposite pubic body at the pubic symphysis. Superior pubic ramus: extends laterally from the body to form part of the acetabulum. Inferior pubic ramus: projects towards the ischium. Together, the superior and inferior rami enclose part of the obturator foramen, through which the obturator nerve, artery and vein pass through to reach the lower limb (Figure 6.3). 37 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Figure 6.3: The bony landmarks of the pubis. The Ischium The ischium forms the posteroinferior part of the hip bone. Much like the pubis, it is composed of a body, an inferior ramus and superior ramus. The inferior ischial ramus combines with the inferior pubic ramus forming enclosed part of the obturator foramen (Figure 6.4). When sitting our body weight falls on the posterior inferior aspect of the ischium known as ischial tuberosities. Figure 6.4: The bony landmarks of the ischium. 38 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) The hip bones have three main articulations: Sacroiliac joint: articulation with the sacrum. Pubic symphysis: articulation between the left and right hip bones. Hip joint: articulation with the head of femur (Figure 6.5). Figure 6.5: the hip bones within the pelvis shows the articulations. Femur: The femur is the only bone in the thigh and the longest bone in the body. It acts as the site of origin and attachment of many muscles and ligaments, and can be divided into three parts; proximal, shaft and distal. Proximal End of Femur: The proximal aspect of the femur articulates with the acetabulum of the pelvis to form the hip joint. It consists of a head and neck, and two bony processes: the greater and lesser trochanters. There are also two bony ridges connecting the two trochanters; the intertrochanteric line anteriorly and the trochanteric crest posteriorly (Figure 6.6). 39 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Figure 6.6: The bony landmarks of proximal femur. 40 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) The Shaft: The shaft of the femur descends in a slight medial direction. This brings the knees closer to the body’s center of gravity, increasing stability. Distal: The distal end of the femur is characterized by the presence of the medial and lateral condyles, which articulate posteriorly with the tibia, and anteriorly with patella to form the knee joint. There is a deep notch on the posterior surface of the femur, between the two condyles known as intercondylar fossa (Figure 6.7). Figure 6.7: The bony landmarks of distal femur. The patella 41 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) The patella (kneecap) is located at the front of the knee joint. Its superior aspect is attached to the quadriceps tendon and inferior aspect to the patellar ligament. It protects the anterior aspect of the knee joint from physical trauma and enhances leg extension. The posterior surface of the patella articulates with the femur, and is marked by two facets: Medial facet: articulates with the medial condyle of the femur. Lateral facet: articulates with the lateral condyle of the femur (Figure 6.8). Figure 6.8: The bony landmarks patella. Tibia: The tibia is the main bone of the lower leg, forming what is more commonly known as the shin (Figure 6.9). Figure 6.9: The anatomical position of the tibia. 42 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) The proximal tibia is widened by the medial and lateral condyles, which aid in weight-bearing. The condyles form a flat surface, known as the tibial plateau (Figure 6.10). This structure articulates with the femoral condyles to form the key articulation of the knee joint. Figure 6.10: Tibia plateau The shaft of the tibia is prism-shaped, with three borders and three surfaces: anterior, posterior and lateral. The distal end of the tibia widens to assist with weight-bearing. The medial malleolus is a bony projection continuing inferiorly on the medial aspect of the tibia (Figure 6.11). It articulates with the tarsal bone (Talus) to form part of the ankle joint. Laterally is the fibular notch, where the fibula is bound to the tibia forming the distal tibiofibular joint. Figure 6.11: The bony landmarks of distal tibia. 43 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Fibula: The fibula is a bone located within the lateral aspect of the leg. Its main function is to act as an attachment for muscles, and not as a weight-bearer (Figure 6.12). Figure 6.12: The anatomical position of the fibula. Distally, the lateral surface continues inferiorly, and is called the lateral malleolus (Figure 6.13). The lateral malleolus is more prominent than the medial malleolus, and can be palpated at the ankle on the lateral side of the leg. Figure 6.13: Anatomical landmarks of the fibula. It has three main articulations: Proximal tibiofibular joint: articulates with the lateral condyle of the tibia. Distal tibiofibular joint: articulates with the fibular notch of the tibia. Ankle joint: articulates with the talus bone of the foot. 44 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Foot: The bones of the foot provide mechanical support for the soft tissues; helping the foot withstands the weight of the body whilst standing and in motion. They can be divided into three groups: Tarsals: a set of seven irregularly shaped bones. They are situated proximally in the foot in the ankle area. Metatarsals: connect the phalanges to the tarsals. There are five in number, one for each digit. Phalanges: the bones of the toes. Each toe has three phalanges: proximal, intermediate, and distal (except the big toe, which only has two phalanges) (Figure 6.14). Figure 6.14: The bones of the human foot. The tarsal bones (Figure 6.15) of the foot are organized into three rows: proximal, intermediate, and distal. Proximal row (hindfoot): comprises Talus, and Calcaneus (heel bone). The intermediate row (midfoot): contains one bone, the navicular. The distal row (midfoot): there are four tarsal bones, the cuboid and the three cuneiforms. 45 Dr. Ayman Hajjar Anatomy of Head & Neck (Lec.6) Figure 6.15: The tarsal bones of the foot. 46