Anatomy Course Module 2 Sample

Module Two Course Index

Lesson 1:

Anterior Thigh

Lesson 2:

Medial Thigh

Lesson 3:

Posterior Thigh

Quiz

Lesson 4:

Gluteal Region

Quiz

Module Two Lesson One The anterior compartment of the thigh App: Copy of click the link to view a 3 minute video on the anterior thigh organization and muscles- https://3d4medic.al/FBnkzP31 SEARCH TIP To explore any of the muscles below in detail, go to your hub/home screen and click the “Models” tab. In the top right corner, enter the name of the muscle in the search tab. Use your mouse to explore it in 3D detail especially when building the muscle on your skeleton.

Anatomy • The three compartments of the thigh, anterior, medial and posterior are divided by intermuscular septa that pass deeply between the muscle’s groups inner surface of the fascia lata to the linea aspera of the femur. See Image A. • The large anterior compartment of the thigh contains the anterior thigh muscles -the flexors of the hip and the extensors of the knee • The hip flexor group includes the pectineus, psoas major, illiacus, sartorius and rectus femoris. (The tensor fascia latae is part of the gluteal group and will be included with that group.) See Image B. • Note that in image A, the proximal flexors of the hip, the pectineus, psoas major and illiacus are not visible. Their insertions do not extend down the shaft of the femur. The sartorius and quadriceps femoris are two joint muscles able to flex the hip and act on the knee.

IMAGE A

Pectineus • The pectineus is a flat quadrangular muscle located in the anterior part of the superomedial aspect of the thigh. See Image C & D. • The pectineus is a transitional muscle between the anterior and medial compartments.

IMAGE C

Image C. Pectineus anterior view

IMAGE D

Image D. Pectineus posterior view

Iliopsoas • The iliopsoas is the chief flexor of the thigh, the most powerful of the hip flexors with the longest range. Image E and F. • Most of its mass located in the posterior wall of the abdomen and greater pelvis.

• It is the only muscle attached to the vertebral column, pelvis, and femur.

• It is in a unique position not only to produce movement but to stabilize (fixate).

• C oncentric contraction of the iliopsoas typically moves the free limb, producing flexion at the hip to lift the limb and initiate its forward swing during walking (i.e. during the pre-swing and initial swing phases) as the opposite limb accepts weight or to elevate the limb during climbing.

Vastus Muscles The names of the three large vastus muscles (vasti) indicate their position around the femoral shaft. Image O. • Vastus lateralis, the largest component of the quadriceps, lies on the lateral side of the thigh. • Vastus medialis covers the medial side of the thigh. • Vastus intermedius lie deep to the rectus femoris, between the vastus medialis and vastus lateralis.

It is difficult to isolate the function of the three vastus muscles.

IMAGE O

Module Two Lesson Two The medial compartment of the thigh App: Click or copy the link to view a 3 min. video on the medial thighhttps://3d4medic.al/RVitIApn

The Anatomy • The muscles of the medial compartment of the thigh comprise the adductor group, consisting of the adductor longus, brevis, magnus, gracilis and obturator externus.

• In general, they attach proximally to the anteroinferior external surface of the bony pelvis and distally to the linea aspera of the femur (images below).

• Their actions are more complex than pulling the thigh towards the midline of the body. From the anatomical position, the main action of the adductor group is to pull the thigh medially, toward or past the median plane, e.g., pulling the legs together when riding a horse. This is known as frontal plane movement.

• With the leg in flexion they can assist with extension and with the leg in extension, they can assist with flexion. This is described as sagittal plane function.

• They are also used to stabilize the stance when standing on both feet and to correct a lateral sway of the trunk.

• The adductor compartment constitutes a large muscle mass. They are separated from the anterior and posterior compartments by fascial intermuscular septa.

Table 1. Muscles of medial thigh: Adductors of thigh Muscle1

Proximal Attachment

Distal Attachment

Innervation

Main Action

Adductor longus

Body of pubis inferior to pubic crest

Middle third of linea aspera of femur

Adductor brevis

Body and inferior ramus of pubis

Pectineal line and proximal part of linea aspera of femur

Adductor magnus

Adductor part: inferior ramus of pubis, ramus of ischium

Adductor part: gluteal tuberosity, linea aspera, medial supracondylar line Hamstring part: adductor tubercle of femur

Adductor part: obturator nerve (L2, L3, L4), branches of posterior division Hamstring part: tibial part of sciatic nerve (L4)

Adducts thigh Adductor part: flexes thigh

Hamstrings part: ischial tuberosity

Obturator nerve, branch of anterior division (L2, L3, L4)

Adduct thigh

Adduct thigh; to some extent flexes it

Hamstring part: extends thigh

Gracilis

Body and inferior ramus of pubis

Superior part of medial surface of tibia

Obturator nerve (L2, L3)

Adducts thigh; flexes leg; helps rotate leg medially

Obturator externus

Margins of obturator foramen and obturator membrane

Trochanteric fossa of femur

Obturator nerve (L3, L4)

Laterally rotates thigh; steadies head of femur in acetabulum

Collectively, the five muscles listed are adductors of the thigh, but their actions are more complex (e.g., they act as flexors of the hip joint during flexion of the knee joint and are active during walking).

1

Module Two Lesson Three The posterior compartment of the thigh App: Click or copy the link to view a 3 min. video on the posterior thighhttps://3d4medic.al/3NkYijRb The hamstrings received their name because it is common to tie hams (pork thighs) up for curing and/or smoking with a hook around these muscle tendons. This also explains the expression “hamstringing the enemy” by slashing these tendons lateral and medial to the knees.

The Anatomy • The muscles in the posterior compartment of the thigh are hamstrings.

• The hamstrings are separated from the anterior compartment of the thigh by the lateral intermuscular septum.

• Deep to the hamstrings on the posterior thigh is the adductor magnus, which is also separated from the posterior compartment by deep fascia.

• The hamstring muscles are:1) semitendinosus, 2) semimembranosus and 3) biceps femoris (long head). See Image A.

IMAGE 5

Gluteus Maximus • The gluteus maximus is the most superficial gluteal muscle.

• It is the heaviest, largest and most coarsely fibered muscle of the body.

• The gluteus maximus covers all the other gluteal muscles except for the anterior superior third of the gluteus medius. (see image 6) • The gluteus maximus slopes inferior laterally at a 45 degree angle from the pelvis to the buttock. The fibers of the superior and larger part insert into the iliotibial tract and indirectly, via the lateral intermuscular septum, into the linea aspera of the femur.

• Some deep fibers of the inferior part of the muscle insert to the gluteal tuberosity of the femur. Image 6 & 7.

Adductor Longus The adductor longus is a large fan-shaped muscle and is the most anteriorly placed of the adductor group. See images C & D. IMAGE C

IMAGE D

Image C. Anterior

Adductor Brevis

Image D. Posterior IMAGE E

The adductor brevis, is the short adductor, lies deep to the pectineus and adductor longus where it arises from the body and inferior ramus of the pubis.

See image E.

Image E. Anterior view Brevis

When the knee is flexed to 90°, the tendons of the lateral hamstrings (biceps), as well as the iliotibial tract, pass to the lateral side of the tibia. In this position, contraction of the biceps and tensor fasciae latae produces about 40° lateral rotation of the tibia at the knee. Image D. Rotation of the flexed knee is especially important for example in snow skiing and changing directions rapidly during running.

IMAGE D

Image D. The short and long heads of bicpes can externally rotate the tibia with the knee flexed.

IMAGE E

Semitendinosus The semitendinosus, as its name indicated, is half tendinous (Image E). It has a fusiform belly that is usually interrupted by a tendinous intersection and a long, cordlike tendon that begins approximately two thirds of the way down the thigh.

Distally, the tendon attaches to the medial surface of the superior part of the tibia as part of the pes anserinus formation in conjunction with the tendinous insertions of the sartorius and gracilis.

IMAGE 6

The main actions of the gluteus maximus are extension and lateral rotation of the thigh.

When the distal attachments of the gluteus maximus is fixed, the muscle extends the trunk on the lower limb. Although it is the strongest extensor of the hip, it acts mostly when strong force is necessary for example, standing from sitting, fast running and walking up stairs.

IMAGE 7

Because the iliotibial tract crosses the knee and attaches to the anteriorlateral tubercle of the tibia, the gluteus maximus (and tensor fascia latae) are able to assist in making the extended knee stable.

Image 6 & 7.

Note the attachments of the gluteus maximus into both the Iliotibial tract and the gluteal tuberosity on the posterior of the femur.