Carnivore Anatomy Lab 21 Introduction

CONTENTS:

Lab Objectives
Anatomical Terms
Instructor Commentary
Dissection Steps
Dissection Videos
Dissection Images

Lab Objectives:

Medial View

• Find nerves that innervate the pelvic limb:
- obturator nerve (to medial thigh muscles)
- femoral nerve (to cranial thigh muscles) & saphenous n. (medial limb)

Lateral View

• Find nerves from sacral plexus to pelvis:
      - pudendal nerve (SE and GSA to/from pelvic organs)
      - pelvic nerve (VE and GVA to/from pelvic organs)
      - caudal cutaneous femoral nerve

• Find nerves that innervate the pelvic limb:
      - lumbosacral trunk (L6, L7, & S1)
            -- cranial gluteal n. (gluteal & tensor fasciae latae mm.)
            -- caudal gluteal n. (superficial gluteal m.)
      - sciatic (ischiatic) n. (L6, L7, S1, & S2 )
            -- tibial n. (caudal muscles of crus & plantar pes sensation)
            -- common fibular (peroneal) n., divides into: superficial & deep fibular (peroneal) nn.
                        (cranial muscles of crus & dorsal pes sensation)

• Optionally, dissect lumbosacral plexus (L4 to S3 ventral branches),
located within sublumbar musculature and in the pelvic cavity.

• Arteries of the pes:
      - dorsal pedal a. = cranial tibial a. re-named in the pes (foot)
            -- arcuate a.
                  - perforating branch

CONTENTS

Anatomical Terms:

Pelvic Limb: nerves
        Lumbosacral Plexus:
                obturator nerve
                femoral nerve
                        saphenous nerve
                pudendal nerve
                        caudal rectal nerve
                        perineal nerves
                        dorsal nerve of the penis (clitoris)
                caudal cutaneous femoral nerve (do not ned to identify)
                lumbosacral trunk
                        cranial gluteal nerve
                        caudal gluteal nerve
                sciatic nerve
                        common fibular (peroneal) nerve
                                lateral cutaneous sural n.
                                superficial fibular (peroneal) n.
                                deep fibular (peroneal) nerve
                                        dorsal digital nn.
                        tibial n.
                                caudal cutaneous sural nerve
                                plantar digital nn.

Pes: arteries
        dorsal pedal a.
                arcuate a.
                        dorsal metatarsal aa.
                                perforating branch
                                        plantar digital aa.

        Note:
             coxa [Latin = hip] e.g., os coxae = bone of the hip
             ischium [Latin & Greek ischion = hip] - caudal part (bone) of hip bone
             sciatic [Latin: sciaticus = pertaining to the ischium]
             ischiatic [Latin: ischiaticus = pertaining to the ischium]
             saphenous [Greek: saphaina = manifest, seen clearly]
             peroneal [Latin: peroneus = fibula]

CONTENTS

Instructor Commentary:

The lumbosacral plexus which innervates the pelvic limb and pelvis, is formed by ventral branches of spinal nerves L4 to S3 in the carnivore. These ventral branches exchange axons and give rise to individual nerves that contain axons from multiple segments. The lumbar portion of the lumbosacral plexus is located inside sublumbar musculature.

Innervation of the pelvic limb may be summarized as follows: The obturator n. innervates medial (adductor) muscles. The femoral n. innervates cranial muscles of the thigh. All remaining muscles of the limb are innervated by the sciatic n. After sending branches to the hamstring muscles, the sciatic innervates muscles of the crus with two branches: the tibial n. to caudal muscles and the common fibular (peroneal) n. to cranial muscles. Note: The sciatic nerve arises from the lumbosacral trunk, which is formed by L6, L7 & S1. The trunk becomes sciatic n. after it is joined by the S2 ventral branch, which occurs after the trunk gives off the cranial & caudal gluteal nerves.

The sacral portion of the lumbosacral plexus gives rise to two principal nerves (in addition to cutaneous nerves): The pelvic n. carries parasympathetic visceral efferent innervation to pelvic viscera (smooth muscle and glands) and general visceral afferents from the viscera. The pudendal n. carries somatic efferent innervation to anal and urethral voluntary sphincters and general somatic afferent innervation from pelvic structures including the anus and penis/clitoris.

NOTE: The lumbosacral plexus paragraph in Guide to the Dissection of the Dog (p.195) states that the lumbosacral plexus begins with the L1 ventral branch (which is official NAV terminology). However, with one exception, the first three lumbar ventral branches run independently. The actual plexus begins at L4 (L4 through S3). The one exception is that genitofemoral nerve fibers commonly arise from L3 & L4.

CONTENTS

Dissection Steps:

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Dissection Videos:

CONTENTS

Dissection Images:

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