Dissection of deep hip and tail of the rat, BAA 289L 2004

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Hip and Tail

Deep Hip and Tail of the Rat (Rattus norvegicus)

Photos and text by Yu Jin Kim and Ana Panduro

Part I: Deep Hip Muscles

Dissection Notes:

The muscles of the hip are tightly spread over the ilium, the ischium, and the trochanters of the femur. In order to see any of the deep hip muscles, a lot of superficial and deep muscles had to be removed out of the way. The removal of the gluteus medius and the gluteus minimus was easy because the gluteus maximus had been previously removed in the hindleg lab. We lifted the lateral edges of the glutei upwards and used a scalpel to slice the medial attachments on the lumbodorsal muscles and ilium. In addition, all muscles attached to the femur were cut or pulled off. This was done to see the hip muscle attachments to the greater and lesser trochanters of the femur.

Discussion and Comparison

Our hip rotators were very well developed and easily differentiable, more so than the human deep hip rotators. The gemelli, the iliopsoas, and the obturators were especially large. This is probably because as a plantigrade quadruped, the rat has a greater degree of hip rotation and a greater degree of motion than humans. But compared to the other animals in the lab, our hip rotators are just as well developed as the rest, except for the fetal pig, whose muscles were not differentiable at all. This is probably because most of the animals in lab are quadrupeds.

Part II.

Our specimen’s tail extends 20 centimeters and is equally as long as the rat’s length from nose to anus (also 20 centimeters). The rat’s tail is used mainly for balance. Unlike the opossum, it has no prehensile ability. However, like the beaver, the tail may aid in balancing the rat while swimming in water. Unlike the beaver’s tail, however, it is not anywhere near as specialized as the beaver tail to maneuver and propel the animal around the water. Also like the beaver, the rat’s tail is made of hundreds of little scales that can better be seen under the microscope. Each scale has several follicles of tiny hairs attached to them, all of which are pointing towards the tip of the tail (caudally). The scales on the beaver are larger, darker, and have less hair attached.

[1, 2]

	Origin	Insertion	Action
Quadratus lumborum	centra of posterior thoracic and lumbar vertebrae	ilium	bends body laterally
Iliopsoas
a. Psoas major	lumbar vertebrae	lesser trochanter of femur	flexes hip
b. Psoas minor	centra of posterior thoracic and anterior lumbar vertebrae	pelvic girdle	flexes back
c. Iliacus	deep surface of the ilium	lesser trochanter of the femur	flexes hip

[1, 2]

	Origin	Insertion	Action
Gemellus superior	ilium , ischium	greater trochanter of femur	rotate and abduct leg
Gemellus inferior	lateral surface of ischium	tendon of obturator internus	abducts leg
Obturator internus	ischial ramus	lesser trochanter	abducts legs
Obturator externus	pubis and ischium	trochanteric fossa of femur	rotates and protracts leg
Quadratus femoris	ischial tuberosity	lesser trochanter	abducts legs

[1, 2]

	Origin	Insertion	Action
Piriformis	sacral and caudal vertebrae	greater trochanter of femur	abducts leg

References:

1. Pelvis and Tail Lab Handout for BAA 289. Dr. Anne Weil. Duke University. Spring Semester 2004

2. Hebel, Rudolf and Melvin W. Anatomy and Embryology of the Laboratory Rat. Stromberg. 1986. BioMed Verlag, Germany.

Artwork: Weil, from Stubbs' 1776 "Anatomy of the Horse."
Background free from Eos Development, with slight color modification.