WEEK 3: Lower limb muscle groups

Question 1

The thigh is divided into 3 main compartments: Anterior, posterior and medial compartment.

State all the muscles of the anterior compartment.

What is their innervation.

Answer 1

1. Iliopsoas muscle: Illiacus and psoas major
2. Quadratus femoris muscle: rectus femoris, vastus lateralis, intermedius and medialis
3. Sartorius muscle
4. Pectineus muscle

Question 2

Describe the iliacus and psoas major muscle UNDER THE FOLLOWING.

1. Origin
2. Insertion
3. Action
4. Innervtion

Answer 2

ORIGIN:
The psoas major originates from the lumbar vertebrae.
The iliacus originates from the iliac fossa of the pelvis.

INSERTION:
They insert together onto the lesser trochanter of the femur.

ACTION:
Flexion of the thigh at the hip joint.

INNERVATION:
The psoas major is innervated by anterior rami of L1-3, while the iliacus is innervated by the femoral nerve (L2-L4).

Question 3

The quadriceps femoris consists of four individual muscles. Outline them.

Where do they insert?

Describe their origins, function and innervation.

Answer 3

The three vastus muscles and the rectus femoris.

The four muscles collectively insert onto the patella via the quadriceps tendon.

1. Vastus Lateralis
   * Proximal attachment: Originates from the greater trochanter and the lateral lip of linea aspera of the femur.
   * Actions: Extension of the knee joint. It has a secondary function of stabilising the patella.
2. Vastus Intermedius
   * Proximal attachment: Originates from the anterior and lateral surfaces of the femoral shaft.
   * Actions: Extension of the knee joint. It has a secondary function of stabilizing the patella.
3. Vastus Medialis
   * Proximal attachment: Originates from the intertrochanteric line and medial lip of the Linea aspera of the femur.
   * Actions: Extension of the knee joint. It has a secondary function of stabilizing the patella.
4. Rectus Femoris
   * Attachments: Originates from the anterior inferior iliac spine and the ilium of the pelvis.
   * Actions: Extension of the knee joint and flexion of the hip joint (it is the only muscle of the quadriceps group to cross both the hip and knee joints).

All innervated by the femoral nerve.

Question 4

• Attachments: Originates from the anterior superior iliac spine, and attaches to the superior, medial surface of the tibia.
• Actions: At the hip joint, it is a flexor, abductor and lateral rotator. At the knee joint, it is also a flexor.
• Innervation: Femoral nerve.

Name the above-described muscle of the anterior compartment.

Answer 4

Sartorius muscle

Question 5

Describe the INSERTION, ACTION and INNERVATION OF THE Pectineus muscle.

Answer 5

• Attachments: Originates from the pectineal line of the pubis bone. It inserts onto the pectineal line on the posterior aspect of the femur, immediately inferior to the lesser trochanter.
• Actions: Adduction and flexion at the hip joint.
• Innervation: Femoral nerve. May also receive a branch from the obturator nerve.

Question 6

The muscles in the medial compartment of the thigh are collectively known as the hip adductors.

State the 5 muscles in this group.

Describe their innervation.

Answer 6

There are five muscles in this group: gracilis, obturator externus, adductor brevis, adductor longus and adductor magnus.

All the medial thigh muscles are innervated by the obturator nerve, which arises from the lumbar plexus. Arterial supply is through the obturator artery.

Question 7

The adductor magnus is the largest muscle in the medial compartment of the thigh.
It is comprised of two parts – an adductor component and a hamstring component.

State their actions and innervation.

Answer 7

• Actions:
  o Adductor – Adduction and flexion of the thigh
  o Hamstring – Adduction and extension of the thigh.
• Innervation:
  o Adductor – Obturator nerve (L2-L4)
  o Hamstring part – Tibial component of the sciatic nerve (L4-S3).

Question 8

Name the landmark formed by the adductor and hamstring part of the adductor magnus muscle.

What is its significance?

Answer 8

Adductor hiatus

The adductor hiatus is a gap or opening in the adductor magnus muscle, which allows for the passage of the femoral vessels (artery and vein) as they transition from the anterior thigh to the popliteal fossa behind the knee.

They change their names to popliteal vessels.

Femoral artery»»Popliteal artery
Popliteal vein»»Femoral vein

Question 9

Name the muscle of the medial compartment that forms the medial border of the femoral triangle.

Answer 9

The adductor longus is a large, flat muscle. It partially covers the adductor brevis and magnus.

Question 10

The adductor brevis is important as a landmark for what?

Answer 10

It separates the anterior and posterior branches of the obturator nerve and is an important anatomical landmark within the medial thigh.

Question 11

The obturator externus is one of the smaller muscles of the medial thigh and it is located superiorly within the compartment.

State its function.

Answer 11

Adduction and lateral rotation of the thigh.

Question 12

The gracilis is the most superficial and medial of the muscles in this compartment. It crosses at both the hip and knee joints.

State its function.

Answer 12

Adduction of the thigh at the hip and flexion of the leg at the knee.

Question 13

What is the femoral triangle?

State the boundaries of the femoral triangle.

State the contents of the femoral triangle.

Answer 13

The femoral triangle is a key anatomical region located in the upper thigh.

It is formed by the boundaries of several muscles and is an important area for understanding vascular access and nerve distribution in the lower limb.

1. Inguinal Ligament (Superior Boundary): The inguinal ligament is a fibrous band that runs from the anterior superior iliac spine to the pubic tubercle. It forms the upper boundary of the femoral triangle.
2. Sartorius Muscle (Lateral Boundary): The sartorius is a long, strap-like muscle that runs obliquely 1. across the thigh. Its tendon forms the lateral boundary of the femoral triangle.
3. Adductor Longus Muscle (Medial Boundary): The adductor longus muscle is located medially and forms the medial boundary of the femoral triangle.
4. FLOOR: Iliopsoas muscle and pectineus muscle

CONTENTS
Within the femoral triangle, important structures include:

Femoral Nerve: The femoral nerve runs through the femoral triangle, providing motor and sensory innervation to the anterior thigh muscles and skin.

Femoral Artery and Vein: These vessels pass through the femoral triangle. The femoral artery is a major vessel that supplies blood to the lower limb, while the femoral vein accompanies it.

Femoral Canal: This is a potential space in the femoral triangle that allows for the passage of structures, such as lymphatic vessels.

Femoral Ring: An opening within the femoral canal, which is a site of potential herniation.

MNEUMONIC

1. THE CONTENTS
   = NAV (Nerve, artery and Vein from LATERAL to MEDIAL)
2. BORDERS
   =SAIL (Satorius, Adductor longus and inguinal ligament)

Question 14

The muscles in the posterior compartment of the thigh are collectively known as_____________.

State their functions.

What is their innervation?

Describe the blood supply.

Answer 14

The muscles in the posterior compartment of the thigh are collectively known as the hamstrings.

They collectively act to extend at the hip and flex at the knee.

These muscles are innervated by the sciatic nerve (L4-S3), with arterial supply from the inferior gluteal artery and perforating branches of the deep femoral artery.

Question 15

The muscles located within the posterior compartment of the thigh are the:

1.
2.
3.
Name a muscle located in the medial thigh which has a similar action to these muscles.

Answer 15

The muscles located within the posterior compartment of the thigh are the biceps femoris, semitendinosus and semimembranosus.

Note: The hamstring portion of the adductor magnus has a similar action to these muscles but is located in the medial thigh.

Question 16

State the functions of the Hamstrings.

Answer 16

1. The biceps femoris has two heads (long head and short head) and is the most lateral of the muscles in the posterior thigh. The common tendon of the two heads can be palpated laterally within the popliteal fossa (posterior knee region).

Attachments: The long head originates from the ischial tuberosity of the pelvis. The short head originates from the linea aspera on posterior surface of the femur. Together, the heads form a tendon, which inserts into the head of the fibula.

Actions: Main action is flexion at the knee. It also extends the thigh at the hip, and laterally rotates at the hip and knee.

Innervation: Long head innervated by the tibial part of the sciatic nerve, whereas the short head is innervated by the common fibular part of the sciatic nerve.

2. Semitendinosus
   The semitendinosus is a largely tendinous muscle. It is situated on the medial aspect of the posterior thigh and superficial to the semimembranosus.

Attachments: Originates from the ischial tuberosity of the pelvis and attaches to the medial surface of the tibia.

Actions: Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.

Innervation: Tibial part of the sciatic nerve.

3. Semimembranosus
   The semimembranosus muscle is flat and broad. It is located deep to the semitendinosus on the medial aspect of the posterior thigh.

Attachments: Originates from the ischial tuberosity (more superiorly than the origin of the semitendinosus and biceps femoris). Attaches to the medial tibial condyle.

Actions: Flexion of the leg at the knee joint.

Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.
Innervation: Tibial

Question 17

The bicep femoris has 2 heads.
Describe their attachments.
Describe their innervation.

Answer 17

Attachments: The long head originates from the ischial tuberosity of the pelvis. The short head originates from the Linea aspera on posterior surface of the femur. Together, the heads form a tendon, which inserts into the head of the fibula.

Innervation: Long head innervated by the tibial part of the sciatic nerve, whereas the short head is innervated by the common fibular part of the sciatic nerve.

Question 18

Where do all muscles of the posterior compartment of the thigh originate from?

Describe the clinical relevance related to this.

Answer 18

1. The muscles of the posterior thigh all originate from the ischial tuberosity of the pelvis.
2. Clinical Relevance: Hamstring Avulsion Fracture of the Ischial Tuberosity

An avulsion fracture occurs when a fragment of bone attached to a ligament or tendon is pulled away from the main mass of the bone.

The muscles of the posterior thigh all originate from the ischial tuberosity of the pelvis. In rare cases (predominantly adolescents), sudden and forceful contraction of the hamstrings can result in an avulsion fracture of the ischial tuberosity.

Question 19

FEMORAL NERVE

State the nerve roots for the femoral nerve.

At what landmark does it enter the anterior compartment of the thigh?

Describe the relation of the femoral nerve to the artery and the vein.

Name the nerve that the femoral nerve continues to the toe cutaneous as.

Describe the effects of INJURY to the femoral nerve.

Answer 19

The femoral nerve is derived from the lumbar plexus, and it is primarily composed of nerve fibers from the anterior divisions of the ventral rami (nerve roots) of the lumbar spinal nerves.

Specifically, the femoral nerve arises from the nerve roots of L2, L3, and L4.

These nerve roots contribute fibers that come together to form the femoral nerve as it descends down the thigh.

Femoral triangle

NAV (Lateral to Medial): Femoral: Nerve, Artery and Vein

Continues to the toe as saphenous nerve= cutaneous.

INJURY
*Paralysis of quadriceps femoris muscles
*Loss of sensation on the thigh (anterior and medial) medial leg and the ball of the toe.

Question 20

Describe the muscles of the anterior and posterior compartment function in terms of extension and flexion of the knee and or leg and the hip.

Answer 20

ANTERIOR
*Knee/ leg: extend
*Thigh: flex

POSTERIOR
*Leg: flex
*Thigh: extend

Question 21

State the two main groups of the gluteus muscles and their functions.

Outline the superficial gluteal muscles.

Answer 21

The gluteal muscles can be divided into two main groups:

Large and superficial muscles which mainly abduct and extend the thigh at the hip joint.

These are the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae.

Question 22

Describe the innervation of the superficial gluteal muscles.

Answer 22

The tensor fasciae latae is the only muscle of the group to also cross the knee joint, so it acts on the leg as well.

The superior gluteal nerve (L4, S1) innervates all of these muscles except for the gluteus maximus which is innervated by the inferior gluteal nerve (L5-S2).

Question 23

Origin Gluteal surface of ilium (between anterior and posterior gluteal lines)
Insertion Lateral aspect of greater trochanter of femur
Innervation Superior gluteal nerve (L4, S1)
Function Hip joint: Hip abduction, Thigh internal rotation (anterior part); Pelvis stabilization

Name the following muscle of the superficial gluteal muscles.

Answer 23

Gluteus maximus

Question 24

State the following Key facts about the gluteus minimus muscle.
Origin
Insertion
Innervation
Function

Answer 24

Key facts about the gluteus minimus muscle
Table quiz
Origin Gluteal surface of ilium (between anterior and inferior gluteal lines)
Insertion Anterior aspect of greater trochanter of femur
Innervation Superior gluteal nerve (L4, S1)
Function Hip joint: Hip abduction, Thigh internal rotation (anterior part); Pelvis stabilization

Question 25

State the following Key facts about the gluteus medius muscle.
Origin
Insertion
Innervation
Function

Answer 25

Key facts about the gluteus medius muscle
Table quiz
Origin Gluteal surface of ilium (between anterior and posterior gluteal lines)
Insertion Lateral aspect of greater trochanter of femur
Innervation Superior gluteal nerve (L4, S1)
Function Hip joint: Hip abduction, Thigh internal rotation (anterior part); Pelvis stabilization

Question 26

State the following Key facts about the Tensor fasciae latae.
Origin
Insertion
Innervation
Function

Answer 26

Key facts about the tensor fasciae latae muscle
Table quiz
Origin Anterior superior iliac spine (ASIS), Outer lip of iliac crest
Insertion Iliotibial tract
Innervation Superior gluteal nerve (L4, S1)
Function Hip joint: Thigh internal rotation, (Weak abduction); Knee joint: Leg external rotation, (Weak leg flexion/extension); Stabilizes hip & knee joints

Question 27

Outline the deep gluteal muscles.

Answer 27

Small and deep muscles which mainly externally rotate the thigh at the hip joint and stabilize the pelvis.

These are the piriformis, obturator internus, obturator externus, gemellus superior, gemellus inferior, and quadratus femoris.

They are also known as the inner hip muscles and deep external rotators.

Question 28

State the 2 landmarks formed by the piriformis muscle.

Answer 28

Originating from the anterior surface of the sacrum, it passes posteriorly and inferiorly through the greater sciatic foramen to insert onto the greater trochanter.

As it runs through the greater sciatic foramen, spaces remain above and below the piriformis – the suprapiriform and infrapiriform foramina.

Superior gluteal vessels and nerves pass above the piriformis through the suprapiriform foramen, while inferior gluteal vessels and nerves pass below the piriformis through the infrapiriform foramen. The piriformis is innervated by the nerve to piriformis (S1-S2).

Question 29

State the 3 muscles that form the Triceps coxae.

Answer 29

Gemellus superior, together with obturator internus and gemellus inferior, form a three-headed muscle known as the triceps coxae.

These muscles are not capable of action individually and converge into a common tendon.