These are axial views of the pelvis as seen by Computed Tomography. The numbered lines on the scout view to the far left correspond to the numbered thumbnail images at the bottom. Click on one of these thumbnail images to show a larger numbered version of the image to the near left.

Click on a number or anatomic structure on the image to the left and the text in this frame will advance to the text corresponding to the structure.

1. Aorta.

The aorta continues inferiorly into the lower abdomen and pelvis, bifurcating into the common iliac arteries in front of the 4th lumbar vertebra. This lower portion of the aorta also gives off paired lumbar arteries and the middle sacral artery.

(2) Inferior Vena Cava
The inferior vena cava is a large vein that returns blood from the blood in the lower part of the body.  It is a reservoir for the common iliac, lumbar, right gonadal, renal, right adrenal, and hepatic veins.  It and the superior vena cava empty into the right atrium.  The inferior vena cava assumes a retroperitoneal position to the right of the aorta as it ascends from the abdomen into the thorax. The IVC traverses its own foramen in the diaphragm to enter the thorax.  The foramen is located at at T-8.  Pulmonary emboli often begin as blood clots that develop in the veins of the lower extremities and travel up the IVC, through the heart and into the lungs. A Greenfield filter or other types of filters can be placed in the IVC to trap such emboli before they reach the lung.

(3) Ureter
    The ureter is a tubular structure that receives urine from the kidney and delivers it to the urinary bladder.  It is a long and muscular tube is about 25 cm long in the abdomen and 5mm wide.  The ureter is considered the continuation of the renal pelvis.  It provides peristaltic waves to push the urine to the bladder.  The ureter is a retroperitoneal structure.  As it descends into the pelvis it is located anterior to the psoas muscle. The ureter crosses the pelvic brim at the level of the bifurcation of the common iliac artery.  It then enters the bladder from a posterior and superior aspect and lateral to the ductus deferens in the male.  In the female the ureters are crossed anteriorly by the uterine artery before the ureter enters the bladder.  The pain of ureteral colic is unique in that it is caused by a kidney stone and is classically described as intermittent flank pain radiating to the groin.  As opposed to patients suffering from peritonitis, patients with ureteral colic cannot lie still in bed.

(4) Left Kidney
The left kidney is usually slightly higher than the right kidney. The left renal vein is long and crosses the aorta anteriorly to reach the left kidney. The left kidney rises to as high as the 11th thoracic rib posteriorly.  The kidney has relations with the pancreas, splenic flexure, spleen anteriorly.

(5) Small Bowel
The small intestine is the longest part of the gastrointestinal tract, usually measuring 6-7 meters.  It forms the embryological midgut and is supplied by the superior mesenteric artery. It is divided into duodenum, jejunum, and ileum.  On abdominal x-ray, the small bowel is located towards the center of the abdomen whereas the colon is located at the superior and lateral edge of the abdomen.  The small intestine is identified by valvulae circulares or circular folds of mucosa on barium x-ray study.  It is sometimes referred to as the small bowel.  On this cross sectional image, the small bowel is identified by white coloration due to filling of the barium contrast agent. The organ is responsible for the digestion and absorption of nutrients such as protein and carbohydrates. The terminal ileum is responsible for the absorption of vitamin B12, fatty acids, bile salts. Most digestion of food occurs in the small intestine. In small bowel obstruction caused by either hernias or adhesions, the abdominal x-ray shows multiple dilated loops of small intestine with air-fluid levels seen on upright films.

(6) Cecum
The cecum is the first part of the large intestine. It is about 7 cm. in length. It is located in the right lower quadrant, below the ascending colon. The cecum derives it blood supply from the ileocolic artery, which is a branch of the superior mesenteric artery. The appendix is attached to the part of the cecum that is inferior to the ileocecal junction. The cecum has a unique structure called the ileocecal valve. The ileocecal valve is incompetent in most people because it allows contrast agents introduced through the lower gastrointestinal tract to enter the ileum, which is the last part of the small intestine. The cecum is usually encased by peritoneum and is mobile. This is significant because in chronically constipated patients, the cecum can be a site of volvulus where the cecum twists and moves to the left upper quadrant. This then results in a case of large bowel obstruction which can be life-threatening.  On abdominal x-rays, a cecal volvulus gives an appearance known classically as a bird's peak sign.  In large bowel obstruction, the cecum can enlarge to over 10 cm. in diameter.

(6a) Appendix
    The appendix is a structure that is attached to the cecum about 2.5 cm below the ileocecal junction. It has a length of about 8 cm.  The appendix is longer and narrower in children than in adults.  The organ is sometimes called the vermiform appendix because it resembles a worm. It has no known function and is thought to be a vestigial organ. The appendix is encased in mesentery of the terminal ileum called the mesoappendix. Within the mesoappendix travels the blood vessels that supply blood to the appendix. The blood vessels branch off of the ileocolic arteries, which are themselves branches of the superior mesenteric artery. The position of the organ is variable in that it can be located behind the cecum or behind the ascending colon. As a general rule of thumb during physical examination, the base of the organ is located 2/3's of the distance from a line drawn from the umbilicus to the anterior superior iliac spine. This is known in surgery as McBurney's point.
    In a disease called appendicitis, the appendix is inflamed and it is thought to be caused by obstruction by feces. The patient classically presents with vague abdominal pain which is at first diffuse then localizes to McBurney's point.  Symtpoms also include nausea, vomitting, and loss of appetite. This last symptom is very specific for appendicitis. Treatment with antibiotics and surgery are cures for this disease.  Appendicitis is more common in children than in adults.

(7) Descending Colon
    This part of the colon is also retroperitoneal and derives its blood supply from the left colic branch of the inferior mesenteric artery. The descending, part of the transverse, and sigmoid colon make up the embryological hindgut. The hindgut takes it blood supply form the inferior mesenteric artery. The descending colon is located on the left side of the abdomen and lies along the left paracolic gutter. This part of the colon is connected to the posterior abdominal wall from the splenic flexure to the pelvis.  Its function is in storing stool and absorbing water from the stool to form solid feces.

(8) Psoas Muscle
   This is a muscle that runs from the transverse processes of the lumbar vertebrae to attach to the lesser trochanter of the femur and serves to flex the thigh at the hip. This muscle is located in a retroperitoneal position and is considered one of the muscles of posterior abdominal wall muscle. There are major and minor components of this muscle. The minor component has a longer tendon and attaches to the pelvic brim instead of the lesser trochanter. The psoas minor helps the psoas major flex the hip. If tuberculosis spreads to the lumbar region, it can spread into the fascia enclosing the psoas muscles and form a psoas abscess. The pus from this abscess can spread inferiorly over the pelvic brim into the inguinal ligament.  Since the muscle has important relationships with other abdominal organs such as the pancreas, cancer of the pancreas can also invade the muscle and cause spasms leading to severe pain.

(9) Erector Spinae Muscle
    This is a large muscle located on each side of the spinal column. It is composed of three muscles including the iliocostalis, longissimus, and spinalis muscles. These group of muscles serve to extend the vertebral column. All three originate from a tendon located in the posterior part of the iliac crest and attach to different regions of the superior vertebra. For example, the longissimus part of the erector spinae muscles attaches to the transverse processes of the thoracic and cervical vertebra. It also attaches to the mastoid process. The spinalis muscle attaches to the spinous processes of the superior thoracic vertebra. In patients suffering back pain secondary to back strain, one of the cause is tearing of the erector spinae muscles or its ligaments.

(10) Rectus Abdominus Muscle
      This muscle is considered the principle muscle of the anterior abdominal wall and runs vertically from the xiphoid process to the pubic symphysis and pubic crest. The muscle is divided by the linea alba into two components that are located right in the center of the abdomen. The muscle is wide in the superior location but narrows as it travels to the pubic symphysis. The muscle is enclosed by the rectus sheath, which is the aponeurosis of the the flat abdominal muscles including the external oblique, internal oblique and tranversus abdominus. The rectus abdominis helps to compress the abdomen during coughing and defecating. The muscle stabilizes the pelvis when walking.

(11) External Oblique Muscle
    The external oblique is another muscle of the anterior abdominal wall that originates from the external surfaces of the 5th through 12th ribs and attaches to the linea alba, pubic tubercle and anterior half of the iliac crest. The muscles is the most superficial of the three flat anterior abdominal wall muscles, which also include the internal oblique and transversus abdominus muscles. The external oblique forms an aponeurosis called the linea alba as it meets medially. The direction of the fibers are arranged in a direction that is similar to the way the fingers are pointed as they are inserted in ones pant pockets. This is in distinction to the way the fibers of the internal oblique are arranged. The action of this muscles is to compress the abdomen during defecation and parturition.

(12) Internal Oblique Muscle
    The internal oblique is located in the middle of the anterior abdominal wall muscles which also includ the external oblique and tranversus abdominus muscles. This muscle originates from the anterior two thirds of the iliac crest and inserts into the inferior borders of the 12th ribs and linea alba. It also has an origin at the lateral half of the inguinal ligament. The inferior fibers of this muscle also form with conjoint tendon along with the transversus abdominis muscle. The direction of the fibers are arranged at right angles to the direction of the fibers of the external oblique muscle. This is an important way to distinguish the two muscles during dissection. The action of the internal oblique is to compress the abdomen during defecation and parturition. They also support the organs of the abdomen and form a wall for these organs.

(13) Tranversus Abdominus Muscle
    This muscle originates from the internal surfaces of the 7th - 12th costal cartilages and iliac crest, and lateral third of inguinal ligament and attaches medially along with internal and external obliqe to form the linea alba. The muscle medially makes a contribution to the formation of the rectus sheath which encases the rectus abdominis muscle. This muscle is the deepest of the anterior abdominal wall muscles.

(14) Quadratus Lumborum Muscle
    This muscle is located in a location lateral and posterior to the psoas muscles. It is located adjacent to the transverse processes of lumbar vertebrae. It originates from the medial half of inferior border of the 12th rib and inserts into iliolumbar ligament and internal lip of iliac crest. The muscle extends and flexes the vertebral column.

(15) Vertebra (Body)
    This is the large anterior part of each vertebrae that functions to bear weight. The vertebral bodies get bigger in the lower regions of the lumbar area in order to bear the weight of the upper body. Each vertebral body is separated by a cushion of fibrous tissue called the intervertebral disc composed of the annulus fibrosis and nucleus pulposus. C1 does not have a vertebral body.

(16) Vertebra (Spinous Process)
    The spinous process is the part of the vertebra that is formed by the posterior lamina as they come together posteriorly.  It resembles a vertical plate in the back of the vertebral bodies. This plate gets bigger in the lower vertebral bodies of the lumbar region.  The spinous process is the part of the vertebra that can be palpated in the middle of the back. It is the pointed aspect of the vertebra. The spinous process serves as an attachment point for back muscles and ligaments. C1 does not have a spinous process.

(17) Common Iliac Arteries
    These vessels are the continuation of the abdominal aorta after it bifurcates in the abdomen. They are retroperitoneal in location.  The right and left common iliacs then give rise to the internal and external iliacs in the pelvis. The right common iliac is located anterior to the right common iliac vein. The common iliacs are crossed by the ureters anteriorly as the ureters descend from each kidney down into the pelvis.

(17a) Common Iliac Veins
    The common iliac veins converge to form the inferior vena cava.  The two veins are located posterior and to the right of their counterpart common iliac arteries. The two common iliac veins are formed by the internal and external iliac veins which drain the blood from the pelvis and lower extremity.

(18) Iliac Wing
    The iliac wing is the part of the ilium that resembles a fan. It has a fossa that forms part of the posterior abdominal wall. The ilium forms the top two thirds of the hip bone and the top 2/5 of the acetabulum into which the head of the femur fits. The fossa is also an attachment point for many of the muscles of the pelvis.

(19) External Iliac Vessels
    This is one of the two bifurcations of the common iliac as it descends into the pelvis. The external iliac artery gives rise to the inferior epigrastric and deep circumflex iliac before it becomes the femoral artery. The external iliac provides the main blood supply to the lower limb.

(20) Common Femoral Artery and Vein
    The common femoral artery is a continuation of the external iliac vessels below the inguinal ligament. The vessel is located lateral to the femoral vein and medial to the femoral nerve. This important relationship is highlighted by the nemonic "NAVL", which specifies the location of the structures in the femoral triangle with the most lateral being the Nerve, then Artery, then Vein, then Lymphatics.  The anatomic relationship is important on the medicine wards because this artery is a good source of blood for ABG's (arterial blood gases) while the vein may be used for central line placement. When obtaining blood for an arterial blood gas it is important to remember that the femoral artery is lateral to the femoral vein. The pulse of the common femoral artery is usually palpable.

(21) Superficial Femoral Artery
    This artery provides the blood supply to the lower legs. It is formed by the bifurcation of the common femoral artery. The other branch of the common femoral artery is the profunda (or deep) femoral artery. The superficial femoral artery runs deep to the sartorius muscle and dives into the adductor canal formed by the adductor magnus muscle. The SFA then leaves the canal at an opening called the adductor hiatus (Hunter's canal) and enters the popliteal fossa, continuing as the popliteal artery, which supplies blood to the lower leg. The position of the artery allows this vessel to be vulnerable to gunshot wounds and lacerations. It is also a common site of atherosclerotic plaque formation in people with atheroclerotic artery disease. The blockage of this vessel with a plaque gives the patient symptoms of claudication, which are leg pains that are worsened by walking and relieved by rest. A catheter can be inserted into this vessel and a balloon can be inflated in order to open the clogged vessel. This proceure is called balloon angioplasty.

(22) Deep Femoral Artery
    The deep femoral artery is one of the branches of the common femoral artery and provides blood to the thigh. It leaves the femoral triangle and travels deep to the adductor longus muscle. It then gives off branches called the medial and lateral circumflex femoral arteries which are important sources of blood to the thigh muscles. The medial circumflex is important because it is the blood supply to the head and neck of the femur.

(23) Iliacus Muscle
    This is muscle is located lateral to the psoas major muscle and attaches to the body of the femur below the lesser trochanter. It originates from the iliac crest, iliac fossa and ala of the sacrum. It acts to flex the thigh at the hip joint.

(24) Gluteus Maximus Muscle
    The gluteus maximus is one of the largest muscles of the body. It originates from the external surface of the ala of ilium and dorsum of the sacrum. It attaches to the iliotibial tract and the lateral condyle of the tibia. The muscles acts to extend the thigh and assist in lateral rotation of the thigh. The muscle functions as the main extender of the thigh. It also functions to raise the trunk from a flexed position. The main enervation of the nerve comes from the inferior gluteal nerve. It is used little during walking but is used more during jumping, climbing, and running. In trochanteric bursitis, a bursa that separates the gluteus maximus from the lateral side of the greater trochanter of the femur becomes inflamed and it causes a deep pain in the gluteal and lateral thigh muscles. Ischial bursitis is common in weavers due to the movement of their legs. It is inflammation of a bursa that separates the G. Maximus muscle from the ischeal tuberosity.

(25) Gluteus Medius Muscle
     This muscle is deep to the G.Maximus and its actions include abducting the hip joint. It is important during walking as it is responsible for the tilt of the pelvis. The left G. medius muscle functions to pull the left side of the pelvis down so that the right side does not sag during walking and the right foot can clear the ground. This muscle originates from the external surface of the ilium and attaches to the lateral surface of the greater trochanter of the femur. It gets its enervation from the superior gluteal nerve.

(26) Gluteus Minimus Muscle
    This muscle is the smallest of the gluteus muscles and is the most deeply located. It attaches to the external surface of the ilium and attaches to the anterior aspect of the greater trochanter of the femur. It gets its enervation from the superior gluteal nerve. Its functions are similar to the gluteus medius but the G. minimus plays a larger role in rotating the thigh muscles medially. When the enervation to the muscle is injured such as in poliomyelitis, both the G. maximus and medius cannot pull the pelvis down during walking so that the pelvis falls down on the side that the foot is raised. This gives a peculiar gait known as the gluteus medius limp.

(27) Sacrum
    This bone if formed by the five sacral vertebral that are fused together to form a wedged shape bone that functions to supports the pelvis and transmits the weight of the body into the legs through the sacroiliac joints. The sacrum is one of the three bones making the pelvis; the other are the ischium and ilium. The sacrum has four pairs of foramina on each side which provide exit points for the dorsal and ventral sacral nerves.  The first sacral vertebra has a projection called the sacral promontory, which is important in obstretrics because the distance from the promentory to the superior aspect of the pubic symphysis marks the AP diameter of the pelvis. This provides a measure of whether the baby's head will fit through the birth canal. Fusion of the five sacral vertebra does not start until the 20th year.

(28) Urinary Bladder
    This is a hollow muscle which functions to hold urine. In adults it is located posterior and superior to the pubic bones. In infants the bladder is located in the abdomen. It starts entering the pelvis at about 6 years of age. Until then it is located in the abdomen. An adult bladder is located in the pelvis but it extends into the abdomen when it is full of urine. The bladder is a very distensible organ that has folds called rugae, except in the trigone where it is smooth. The trigone is the triangular shaped area in the base of the bladder.

(29) Sigmoid Colon
    This is the end of the intestine located between the descending colon and the rectum. This part of the colon is encased in mesentery called the sigmoid mesocolon, so that this part of this intestine is mobile. The sigmoid colon is usually located in the upper part of the pelvis, inferior to the small intestines. It is the location of storage of stool before defacation. The arterial supply is from a branch of the inferior mesenteric artery called the sigmoid arteries. The sigmoid colon is a common location of a colon cancers, especially at the rectosigmoid junction.

(30) Rectum
    This is the end and last part of the colon. It is located between the sigmoid colon and the anus. It is located posterior to the urinary bladder in males. In females the rectum is located posterior to the vagina and uterus. It is a site for many cancers of the colon. This part of the colon is considered to be retroperitoneal because it is only partially covered with peritoneum. It is continuous with the anal canal. Part of the blood supply to the rectum comes from the inferior mesenteric artery and the other part comes from the middle rectal branches of the inferior iliac vessels.

(31) Seminal Vesicle
    The seminal vesicle the organ (found only in males) serves to secrete a thick alkaline fluid that mixes with the sperm as they pass into the ejaculatory ducts. The fluid secreted by the seminal fluid makes up most of the ejaculatory fluid produced during orgasm. The duct of the seminal vesicle joins the ductus deferens to form the ejaculatory duct. The duct then joins the prostatic urethra at the posterior end. The seminal vesicle is located posterior to the urinary bladder.

(32) Prostate Gland
    The prostate gland is about the size of the walnut and is located underneath the urinary bladder. The prostate is a glandular organ that makes a thin milky fluid that makes up about 20% of the ejaculate. The prostate has both lateral and middle lobes. In benign prostatic hypertrophy, the prostate grows at the middle lobe and can obstruct the urethra as it passes through the prostate gland. Hypertrophy of the prostate is common in men after the age of 50 and causes symptoms of nocturia, dysuria, and urgency. In prostate cancer, there is enlargement of the lateral lobe of the prostate and this may be palpated during rectal exam. Prostate cancer is common in men after the age of 75 and is a slow growing tumor.

(33) Base of Penis
    This part of the penis consists of the root bulb, and the bulbospongiosus muscle. The bulb of the penis is penetrated by the urethra.

(34) Piriformis Muscle
    This pear shaped muscle is located in the posterior pelvis and functions to laterally rotate and abduct the thigh. It originates from the 2nd through 4th sacral segments and inserts on the greater trochanter of the femur. It and the obturator internus play similar roles in moving the femur.

(35) Ischial Spine
    The ischial spine is the part of the ischium that projects medially and separates the greater sciatic notch superiorly from the lesser sciatic notch. The lesser sciatic notch is located below the ischial spine and above the ischial tuberosity. The sacrospinous ligament spans the greater sciatic notch and forms the greater sciatic foramen. The piriformis muscle and other vessels pass through this foramen to the gluteal region. The sacrotuberous and sacrospinous ligaments cross the lesser sciatic foramen to form the lesser sciatic foramen through which the obturator internus muscle and pudendal nerve pass.

(36) Femoral Head
    The femoral head is the part of the femur that fits into the acetabulum of the pelvis. It has a center called a fovea where the ligament to the head of the femur is attached. The head of femur is attached to the body of femur through the femoral neck.

(37) Greater Trochanter
    This is a large projection of the femur located at the junction of the neck and body of femur. It serves as an important attachment point for large muscles such as the gluteus medius and gluteus minimus muscles.

(38) Rectus Femoris Muscle
    This is one of four muscles making up one of the largest muscle groups in the body, called the quadriceps muscles. This muscle originates from the anterior inferior iliac spine and runs down the thigh to attach to the top of the patella, then via the patellar ligament to the tibial tuberosity. The other muscles forming the quadriceps group of muscles include the vastus lateralis, vastus medialis, and vastus intermedius. They are all enervated by the femoral nerve. They all serve to extend the knee joint in activities such as climbing, jumping, and rising from a chair. In an injury such as a charley horse, the fibers of the rectus femoris are torn away from their attachment to the anterior inferior iliac spine, causing localized pain and stiffness. The result could be the formation of a thigh hematoma at the point of injury. The mechanism of injury is often direct trauma to the muscle such as during a football tackle.

(39) Internal Obturator Muscle
    This muscle forms most of the lateral wall of the pelvis and traverses through the lesser sciatic foramen, attaching to the greater trochanter of the femur. It originates from the ilium and ischium. It is enervated by the nerve to the obturator internus. It functions along with the piriformis muscle to laterally rotate the thigh and hold the head of the femur in place in the acetabulum.

(40) External Obturator Muscle
    This muscle serves to laterally rotate the thigh and also hold the head of femur in the acetabulum. It originates from the obturator foramen in the superior medial part of the thigh and crosses posterior to the femur to attach at the trochanteric fossa. It takes its enervation from the obturator nerve.

(41) Ischiorectal Fossa
    This is a potential space surrounding the anal canal. The walls of the fossae are bounded laterally by the ischium, medially by the anal canal, posteriorly by the sacrotuberous ligament and G. Maximus muscle, and anteriorly by the urogenital diaphragm. The internal pudendal artery and pudendal nerve are found within the fossa. There are also soft fat pads called ischioanal pads located in the fossa.  The fossa is often a site of infection originating from a rectal abscess, or anal sinuses.

(42) Symphysis Pubis
    This is a tough cartilage that joins the two bodies of the two pubic bones. The articular surface is covered by a thin layer of hyaline cartilage, which is connected to the other side by an interpubic disc. In women, the greater thickness of this disc allows more mobility of the pelvic bones, allowing a greater diameter of pelvic cavity during parturition.

(43) Inferior Pubic Ramus
    The pubic bone consists of the body and two ramus bones, the superior and inferior pubic rami. The inferior pubic rami passes posterior and inferior to join the ramus of ischium to form half of the pubic arch.

(44) Ischial Tuberosity
    This is the most inferior part of the ischium. It bears weight of the body when one sits on the chair. The tuberosity is usually covered by the G. maximus when the thigh is extended and uncovered by the G. Maximus as the thigh is flexed.

(45) Gracilis Muscle
    This thin muscle lies in a medial position in the thigh and knees. It is the weakest muscle out of the group of adductor muscles in the thigh. It functions to adduct the thigh and flex the leg. It is the only adductor muscle that crosses the knee joint. It receives its enervation through the obturator nerve.

(46) Sartorius Muscle
    This strap-like muscle is named according to the way that it was used as tailors sit on the floor with their knees crossed. The muscle originates from the anterior superior iliac spine and inserts into the superior part of the medial surface of the tibia. It therefore crosses two joints. It functions to flex, abduct and laterally rotate the thigh at the hip joint. It is a superficial muscle of the anterior thigh. It receives enervation from branches of the femoral nerve.

(47) Adductor Magnus Muscle
    This is the largest of the group of adductors of the thigh. This muscle originates from the inferior ramus of the pubic bone and attaches to the gluteal tuberosity and adductor tubercle of the femur. Because it has two heads, both an adductor and hamstring part, it functions to adduct and flex the thigh. It is enervated by both the obturator and sciatic nerves. There is a hiatus in its attachment to the supracondylar line of femur which allows the femoral vessels to pass into the popliteal fossa.

(48) Adductor Longus Muscle
    This muscle is the most anterior of the adductor group of muscles in the thigh. The muscle originates from the body of the pubis and attaches to the pectineal line and proximal part of the linea aspera of femur. It is enervated by the obturator nerve. Along with the other adductors of the thigh--including the adductor magnus, adductor brevis, and pectineus--this muscle functions to adduct the thigh.

(49) Vastus Lateralis Muscle
    This muscle is one of the four making up the quadriceps group of muscles. It lies on the lateral side of the thigh. It originates from the greater trochanter of the femur and attaches to the patellar ligament. Its functions are to extend the lower leg at the knee joint. See Rectus Femoris muscle.

(50) Vastus Intermedius Muscle
    This is another one of the quadriceps group of muscles. It originates form the anterior and lateral surface of femur and attaches to the patellar ligament. It is located in between the vastus medialis and vastus lateralis as its name implies. See Rectus Femoris muscle for function.

(51) Vastus Medialis Muscle
    This is the part of the quadriceps that lies most medially. It originates from the intertrochanteric line of the femus and attaches to the patellar ligament. Its function is to extend the lower leg at the knee joint. See Rectus Femoris muscle.

(52) Semimembranousus and Semitendinosus Muscles
    This pair of muscles are located in the posterior aspect of the thigh. Along with the biceps femoris, the muscles are known as hamstring muscles. As a group they cross the knee and insert into the tibia. This pair of muscles extends the thigh and also flexes the leg. They also medially rotate the tibia. Hamstring injuries are common in athletes who engage in sports where there is tremendous muscular exertion in running or kicking. It is caused by tearing of the fibers of the hamstring muscles which may give rise to a local collection of blood called a hematoma. After the injury any movement of the muscle causes intense pain.

(54) Tensor Fascia Latae
    The tensor fascia latae arises from the anterior part of the iliac crest close to the anterior superior iliac spine and lies just anterior to the anterior border of the gluteus medius. It is a short straplike muscle whose fibers pass downward and somewhat backward to insert on the iliotibial tract a little below the level of the greater trochanter.

(55) Pectineus Muscle
    This muscle lies just medial to the iliopsoas and forms a large part of the femoral triangle. The femoral vessels lie in front of it, and the medial femoral circumflex artery, arising from the femoral or from the profunda femoris, passes backward between it and the iliopsoas. The pectineus muscle arises from the pecten of the pubis and the bone anterior to the pecten and inserts on the posterior aspect of the femur on the pectineal line.