Part 2: Proximal Pelvic Limb

In the lateral thigh region, attaching to the fascia lata, identify the biceps femoris m. and dissect its borders, but DO NOT cut through/remove the fascia lata! (See DG Fig. 2-41)

• Dissect carefully along the caudal border of the biceps femoris m. to avoid cutting the lateral saphenous v. and to preserve the popliteal lymph node.

  • Using blunt dissection with the tip of a scissors, identify the popliteal lymph node in the fat directly caudal to the stifle.

• Transect the biceps femoris m. proximally (dorsally, near the rump region) and reflect the main muscle mass cranially and then distally (but leave it attached to the fascia lata!)

• Dissection Note: You may see a thin slip of muscle, called the caudal crural abductor m., adjacent to the biceps femoris m. caudally. This muscle is not significant for our dissection purposes, and should be reflected with the biceps femoris m. (See DG Figs. 2-41 and 2-43)

Identify the large sciatic n. deep to the biceps femoris m., coursing caudally over the hip and continuing distally in the hind limb. (See DG Figs. 4-59, 4-61, 4-66, 4-68, and 4-70)

• The sciatic n. gives off numerous branches to the various muscles of the hip and thigh regions and then terminates in a common fibular n. and tibial n. which will be dissected later as you move distally in the limb.(See DG Figs. 4-59, 4-61, 4-66, 4-68, and 4-70)

In the cat, identify the gluteofemoralis (aka caudofemoralis) m. just cranial to the biceps femoris m. (note the dog does not have this muscle). (See Figure 12 in Appendix A ‘Supplemental Feline Notes’; this document will also be posted on the course Canvas site)

Caudal to the biceps femoris m., identify the semitendinosus m. (See DG Figs. 2-41 and 2-42, A & B)

• Dissect the borders of the semitendinosus m. but do not transect it.

  Related Learning Objectives

  • D2.6

   

Moving caudal and medial to the semitendinosus m., identify the semimembranosus m. (See DG Figs. 2-41 and 2-42, A & B)

• Define the borders of the semimembranosus m. but do not transect it.

  • Dissection Note: Medially, you will need to separate/differentiate between the borders of the semimembranosus m. and the gracilis m. The gracilis is a fairly flat, thin muscle on the most medial aspect of the thigh (which you will dissect next).

  • Comment: You may notice that the semimembranosus m. has two bellies, but you need not differentiate these parts.

Identify the gracilis m. on the caudomedial aspect of the thigh region, medial to the semimembranosus m. (See DG Fig. 2-42, A and 2-46)

• Transect the gracilis m. through/near the aponeurotic origin (near ventral midline) and reflect it distally.

Deep to the gracilis m., identify the adductor m. (cranial to the semimembranosus m.). (See DG Fig. 2-42, A & B and 2-46, A & B)

• Comment: The adductor has two parts (magnus et brevis & longus) but it is not necessary to differentiate them.

• Carefully transect the adductor m. at its origin (along/near the ventral midline) but do not transect the underlying external obturator m.

Deep to the adductor m., identify the fan-shaped external obturator m. (In order to see this muscle you need to be sure your entire adductor muscle has been transected and reflected.) (See DG Fig. 2-49)

Identify the small, spindle-shaped pectineus m. on the medial aspect of the thigh, cranial to the adductor m. (See DG Fig. 2-42, A & B, and 2-46, A & B)

• Dissection Note: Dissect the pectineus m. carefully as it can sometimes rip/shred easily (especially in cat specimens where the muscle is quite flattened) and be sure to preserve the femoral vessels just cranial to this muscle.

• After identifying it, transect the pectineus m. through its middle.

Identify the sartorius m. on the craniomedial aspect of the thigh region. (See DG Figs. 2-41, 2-42, A, and 2-46)

• Dissection Note: Notice that the sartorius m. has cranial and caudal parts in the dog, but has one continuous muscle belly in the cat.

On the medial aspect of the thigh region, identify the femoral triangle. The femoral triangle is a shallow, triangular space in the proximal thigh through which the femoral artery and vein run. The major borders of the triangle are formed by the abdominal wall (base of the triangle), the sartorius m. cranially, and the pectineus m. caudally. (See DG Fig. 2-79)

• Identify the femoral artery and femoral vein found within the femoral triangle.

After identifying the femoral triangle, transect sartorius m. through its middle (dog: both parts together) and reflect the distal half of the muscle toward the stifle.

On the medial side of the thigh, return to the femoral a. Continue tracing the femoral a. distally to identify the saphenous a. arising from the femoral a., just proximal to the level of the stifle. The saphenous a. supplies the skin on the medial side of the stifle and terminates in cranial & caudal branches. (See DG Figs. 4-55, 4-63, and 4-64) After the saphenous a. is given off, the femoral a. dives deeper into the hind limb and continues distally.

Running alongside the saphenous a., identify the saphenous n.

• Trace the saphenous n. proximally in the thigh region until you uncover its origin from the femoral n. which arises deep in the proximal muscle mass cranial to the base of the femoral triangle. (See DG Figs. 4-58, 4-65, 4-66, and 4-67)

  • Dissection Note: You should note that the femoral nerve gives off the saphenous nerve much more proximal in the limb than the femoral artery gives off the saphenous artery.

Proximally, near the abdominal wall, identify the femoral n. emerging from the iliopsoas m.; it supplies the iliopsoas and quadriceps mm. and gives rise to the saphenous nerve (that you just dissected), which supplies the skin on the medial aspect of the thigh, leg, and pes. (See DG Figs. 4-58, 4-65, 4-66, and 4-67)

• Dissection Note: The iliopsoas muscle is a sublumbar muscle, and is the major extrinsic muscle of the hind limb. The iliopsoas is a powerful flexor of the hip joint.

  • You should be aware of the best location to view this muscle (seen from the medial side near where the abdominal wall meets the proximal thigh) but you will not be able to visualize/dissect much of it without destroying other vital structures. (See DG Figs. 2-47, B, and 2-51)

  • Comment: The iliopsoas m. will be dissected out for you on one of the demonstration animals to allow for visualization of this muscle. Note that the iliopsoas is a fusion of muscle parts, including the psoas major & iliacus mm., but you need not observe the differentiation between these parts on your specimens.

Return to the femoral v. on the medial aspect of the hind limb. Trace it distally in the limb to identify the medial saphenous vein, which satellites the saphenous artery.

• Comment: You should note that this vein is a common feline venipuncture site (and is sometimes used in small dogs as well). (See DG Figs. 4-56, 4-63, and 4-64)

  Related Learning Objective

  • D2.4

   

On the lateral aspect of the hind limb, just caudal to the stifle, identify the lateral saphenous vein (which does not satellite an artery). (See DG Fig. 4-57) Note that there is a cranial branch and caudal branch from the crus contributing to the formation of the lateral saphenous vein. Identify the cranial branch of the lateral saphenous vein.

• Comment: You should note that the cranial branch of the lateral saphenous vein is a common canine venipuncture site. (This site is not commonly used in the feline since it is very small.)

On the lateral aspect of the limb, identify the tensor fasciae latae m. in the cranial thigh region. This muscle attaches to the fascia lata and is somewhat triangular in shape. (See DG Fig. 2-41)

• Dissection Note: You should note that the tensor fasciae latae m. has two parts, cranial and caudal, (particularly noticeable in the dog). The caudal part is flat and triangular, while the cranial part is longer, thicker and more oval in shape.

  • Comment: While you do not need to differentiate these parts, make sure you are seeing the full extent of the muscle to ensure that you transect it completely in the next step.

• Transect the tensor fasciae latae proximally, through both parts, and reflect it distally toward the stifle, but DO NOT cut through/remove the fascia lata! (Keep both the tensor fasciae latae and the biceps femoris mm. attached to the fascia lata!)

Identify the gluteal mm. in the rump region. This group of muscles has several parts: the superficial, middle, and deep gluteal muscles.

• Identify the superficial gluteal m. which is somewhat flat and is attached proximally via an aponeurosis that covers the middle gluteal m. (See DG Fig. 2-41)

  • Transect the superficial gluteal m. proximally at its aponeurosis and reflect it distally.

  • Carefully avoid cutting the sacrotuberous ligament along the caudal border of the gluteal muscles during this dissection in the dog (cats do not have the sacrotuberous ligament).

    • • • The sacrotuberous ligament is a thickened, collagenous band running from the sacrum to the ischiatic tuberosity. In the dog, the superficial gluteal m. arises from the proximal portion of this ligament. Identify the sacrotuberous ligament in the dog. (See DG. Fig. 2-43 and 2-58)

• Deep to the superficial gluteal m. identify the large middle gluteal m. (See DG Fig. 2-41) This is the largest of the gluteal muscle parts.

  • Clean the borders of the middle gluteal; separate the cranial aspect of the middle gluteal from the underlying deep gluteal m.

  • Transect the entire middle gluteal m. and reflect it distally.

  • Dissection Note: Note that you may see the piriformis m. separate from the main muscle mass as you reflect the middle gluteal. Transect and reflect it with the rest of the middle gluteal if this happens in your specimen. (The piriformis m. is the deep caudal portion of the middle gluteal m.)

• Deep to the middle gluteal m. identify the fan-shaped deep gluteal m. (See DG Figs. 2-43 and 2-48)

Identify the location of the caudal mm. of the hip region that rotate the thigh laterally. This group is made up of the internal obturator m., gemelli mm., quadratus femoris m., and external obturator m. (Note that the external obturator m. was previously identified in this lab, found deep to the adductor m.). The individual muscles are of less importance than identifying the location of the group as a whole. (See DG Figs. 2-43, 2-47, 2-48, and 2-49)

• Comment: The caudal mm. of the hip region will be dissected out for you to observe on one of the demonstration animals.

  • On the demonstration animal, note the fan-shaped internal obturator m. The tendon of this muscle is found caudal to the deep gluteal m. (Note that in the demonstration dogs the sacrotuberous ligament may be cut and reflected to better expose the tendon of the internal obturator m.) (See DG Figs. 2-43 and 2-48)

    • • • Also, observe the bursa (shiny pocket w/fluid intended to reduce friction) under the (transected) tendon of the internal obturator.

  • Note the gemelli mm. (two muscles fused together) that lie under/spill over the internal obturator tendon. (See DG Figs. 2-43 and 2-48)

  • Note the short, thick quadratus femoris m. (Note that this muscle can be seen from both lateral and medial sides.) (See DG Figs. 2-43, 2-47, D, and 2-49)

Comment: Note that there is a pudendal n. that emerges caudolaterally from the pelvic cavity, near the pudendal vessels, medial to the superficial gluteal m. (See DG Figs. 4-65, 4-66, 4-68, and 4-69) While this nerve, and its branches, are particularly difficult to dissect, they are clinically relevant and should be mentioned. Note that these nerves will  be revisited in Chapter 6, when you dissect the pelvic region and genitalia. These nerves WILL NOT be dissected out for you to view at this time and you DO NOT need to dissect them on your specimens – this is simply for your information due to its clinical significance.

• From the pudendal n., a branch called the caudal rectal n. courses to the external anal sphincter m. (which it supplies). (See DG Fig. 4-69)

• Note that there are also perineal nerves arising from the pudendal n. supplying the skin of the anus and perineum, and continuing to the scrotum/labium. (See DG Figs. 4-65, 4-66, 4-68, and 4-69)

• Distally, the pudendal n. gives off the dorsal nerve of the penis (male)/dorsal nerve of the clitoris (female) following alongside/near an artery of the same name.

  • Dissection Note: In the male, the dorsal nerve of the penis will be sizable and easy to trace, while the dorsal nerve of the clitoris in the female may be small and difficult to locate. (In the tomcat, the dorsal nerve of the penis will be located on the ventral surface of the penis (due to the caudally directed penis); you need not trace the dorsal nerve of the clitoris in the queen.)

Identify the cranial mm. of the thigh region that flex the hip and extend the knee. This group is made up of the quadriceps femoris m. and the previously mentioned iliopsoas m.

• On the cranial aspect of the thigh region, identify the quadriceps femoris m. deep to the fascia lata. Be sure that you have transected and reflected your tensor fasciae latae and your sartorius mm. sufficiently to be able to see the different parts of this muscle. The quadriceps femoris has four heads: vastus lateralis, vastus intermedius, vastus medialis, and rectus femoris. This entire muscle is a powerful extensor of the stifle joint, and the rectus femoris part is also a flexor of the hip joint. (See DG Figs. 2-42, B, 2-43, 2-46, B and 2-49)

• Identify the rectus femoris m., which is the most cranial part of the quadriceps femoris m., and the only head with its origin on the pelvis (ilium) rather than originating from the femur. (See DG Figs. 2-42, B, 2-43, 2-46, B and 2-49)

  • Transect the rectus femoris m. through its middle and reflect the proximal part to aid in viewing the other three heads of the quadriceps femoris m.

• Lateral to the rectus femoris m., identify the vastus lateralis m. (See DG Fig. 2-43)

• Medial to the rectus femoris m., identify the vastus medialis m. (See DG Figs. 2-42, B, and 2-46, B)

• Deep to the rectus femoris, and sandwiched between the vastus lateralis and vastus medialis mm., identify the vastus intermedius m. This muscle lies directly on the cranial surface of the femur and may be difficult to separate from the vastus medialis and lateralis mm. in some specimens (especially in cats). (See DG Fig. 2-49)

Locate the stifle (knee) joint. On the cranial aspect of the stifle, note where the patella and patellar ligament are located and be able to identify them. (See DG Fig. 2-60, C & D)

• Comment: The patella is a sesamoid bone embedded in the large tendon of insertion of the quadriceps femoris m. The patellar ligament extends from the patella to the tibial tuberosity and serves as the tendon of insertion of the quadriceps femoris m.

  Related Learning Objective

  • D2.7

   

Using a sharp scalpel, cut proximally around the patella in order to reflect the patella and attached patellar ligament distally to open the stifle (knee) joint.