Download the pelvic girdle and lower limb

THE PELVIC GIRDLE AND LOWER LIMB
I.
BONES OF THE PELVIC GIRDLE AND LOWER LIMB
A.
Bones of the pelvic girdle (Fig. 7.29-7.32) Along with the sacrum, these
two bones form a complete ring. Use disarticulated bones and skeletons
to study these bones.
1.
Coxal bones (Fig.7.30, 7.31) Know right from left. Each coxa
(singular) is formed by the fusion of three irregularly-shaped bones.
Ilium
2.
Ischium
Pubis
Features of the coxal bones
Symphysis pubis
Acetabulum
Anteriorsuperior
iliac spine
Anterior inferior
iliac spine
Pelvic inlet
liac crest
Ischial tuberosity
Ischial spine
Sacroiliac joint
Obturator foramen
Subpubic angle
B.
Bones of the thigh and leg Use the disarticulated bones.
1.
Femur (Fig. 7.33) Know right from left.
Head
Neck
Greater trochanter
(“tro-cant-er”)
Lesser trochanter
2.
Lateral condyle
Medial condyle
Lateral epicondyle
Medial epicondyle
Linea aspera
Patella (Fig. 7.34) You do not need to distinguish right from left.
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3.
Tibia (Fig. 7.35) Know right from left.
Tibial tuberosity
Medial malleolus
(“mal-lee-o-lus”)
4.
Fibula (Fig. 7.35) You do not need to distinguish right from left, but
recognize the proximal end from the distal end.
Head
C.
Lateral malleolus
Bones of the ankle and foot (Fig.7.378) Use the articulated foot bones.
1.
Tarsal bones There are 7, but we will name only the largest two:
Talus
D.
Lateral condyle
Medial condyle
Tibial (anterior) crest
Calcaneus
2.
Metatarsals 1-5 (Numbered from medial to lateral.)
3.
Phalanges (fa lan jeez); singular is phalanx (fay-lanks)
The hallux (digit 1) has a proximal phalanx and distal
phalanx.
Digits 2-5 have a proximal, middle and distal phalanx.
Helpful tips for learning these bones
1.
The “features” of bones (Table 7.2)
Condyle:
the smooth surface of a joint
Crest:
a ridge along a bone
Epicondyle: a rough surface above a condyle for muscle
attachment
Foramen:
an opening in a bone (plural– foramina)
Head:
a more or less round end of a bone
Neck:
a narrow part between two larger parts of a
bone
Notch:
a small cut-out part on a bone
Process:
a part of a bone that projects out
Spine:
a sharp projection of a bone
Trochanter: a large, blunt tuberosity
Tuberosity: a large rough bump where a muscle attaches
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2.
Observe the articulations of the coxal bones on a skeleton. At the
sacroiliac joint, the coxal bone articulates with what other bone?
_________________________________
The head of the femur articulates with what part of the coxal bone?
____________________________
3.
Observe the articulations of the knee on a skeleton. The medial
and lateral condyles of the femur articulate with the tibia’s
________________________ ________________________ and
________________________ ______________________ . Does
the fibula articulate with the femur? (Yes/No) ______ It articulates
with the _____________. Finally, notice the position of the patella.
4.
Observe the articulations of the ankle on a skeleton. The lateral
malleolus of the _________________ and the medial malleolus of
the ___________________ form a strong hinge joint with the
_________________ bone.
5.
How many tarsal bones are there? (Count the talus and calcaneus
as well as the others that we did not name.) _______
Optional notes on the bones of the pelvic girdle and lower limbs
1.
The neck of the femur is the site of a "broken hip." A "complete hip
replacement" is surgery in which a stainless steel head and neck
replaces the proximal portion of the femur, and a "cup" replaces the
acetabulum.
2.
A child's head is said to be "engaged" when it is lodged within the pelvic
inlet prior to its birth.
3.
The ischial spines, if large, can decrease the space available for
passage of the fetus at birth.
4.
The subpubic angle is wider in the female pelvis (greater than 90o ) than
in the male pelvis (less than 90o ). The pelvic inlet in the female is oval
shaped; in the male it is heart-shaped. The female pelvis is wider and
shallower than the male pelvis. For other differences between male and
female pelvises, see Fig. 7.32.
5.
The weight bearing bone of the leg is the tibia. The fibula serves to
stabilize the ankle joint.
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II.
MUSCLES THAT ACT ON THE LOWER LIMB
A.
Movement of the thigh (Fig. 10.31-10.33) Use the torso models, and
lower limb models.
Note that iliopsoas is best seen within the abdomen, on its posterior wall.
1.
Iliopsoas (“il-e-o-so-as”)
(Iliacus and
psoas major)
2.
Gluteus maximus
Origin: Ilium
Insertion: Greater trochanter
Actions: Extends and abducts thigh
3.
Gluteus medius
Origin: Ilium
Insertion: Greater trochanter
Action: Abducts thigh
4.
Adductor group
Origin: Pubis
Insertion: Linea aspera
Actions (2): Adducts and flexes thigh
(Adductor longus,
brevis and magnus)
B.
Origin: Ilium, lumbar vertebra
Insertion: Lesser trochanter
Action: Flexes thigh
Movement of the thigh and leg (Fig. 10.30, 10.33)
1.
Quadriceps femoris group Origin: Femur, anterior inferior iliac
spine
(Rectus femoris
Insertion: Tibial tuberosity
vastus lateralis, etc.)
Actions (2): Flexes thigh; extends leg
2.
Hamstring group
(semimembranosus
semitendinosus,
biceps femoris)
3.
Sartorius
Origin: Ischial tuberosity
Insertion: Tibia and fibula
Action (2): Extends thigh; flexes leg
Origin: Anterior superior iliac spine
Insertion: Tibia
Actions (3): Flexes and laterally
rotates thigh; flexes leg (tailor sitting
position)
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C.
Movement of the foot and toes (Fig. 10.36; 10.37 [10.38, 10.39])
1.
Peroneus (fibularis) longus Actions (2): Plantarflexes and
everts foot
2.
Extensor digitorum
Action: Extends toes
3.
Tibialis anterior
Actions: Dorsiflexes and inverts foot
4.
Flexor digitorum
Action: Flexes toes
5.
Gastrocnemius
Insertion: Calcaneus via Achilles'
tendon
Action: Plantarflexes foot
(A “PET Fat Goldfish” can help you learn names and locations on the leg.)
D.
Anatomy is a precise descriptive science based on observation.
Unlike the common misconception, it is not based on rote memory!
1.
Each name is meant to identify some characteristic of the muscle.
Make the muscle “show” you its name as you observe its location,
shape, size, or action.
2.
On the trunk origins are more medial; insertions are more lateral.
On the limbs origins are more proximal; insertions are more distal.
3.
Make the muscle “show” you its origin or insertion by observing it.
In most but not all muscles, you can see the assigned origin and
insertion on the models.
4.
Muscles on the limbs usually cause movement of the part of the
limb distal to their belly.
5.
Make the muscle “show” you its action by its position. Muscles
cause movement by shortening (contracting), which pulls one bone
toward or away from another bone. Notice the direction of the fibers
of the muscle, which are the parts that shorten.
6.
As you learn each muscle, draw your fingers slowly along the belly
from the origin to the insertion. Say the name. Name the origin and
name the insertion as you touch each end on the models or
yourself. Then, perform the actions with your own muscles as you
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say the name of the actions aloud. In lab, use the models and your
own muscles. At home, use your own muscles.
Optional notes on the muscles that act on the lower limbs:
1.
The gluteus maximus is a common site for intramuscular injections,
since it is the thickest muscle of the body. However, the thickest nerve of
the body, the sciatic nerve, runs deep to the gluteus maximus, making an
understanding of the anatomy essential to know before attempting an
intramuscular injection in this region.
2.
Iliopsoas is located primarily in the posterior wall of the abdomen. It
shortens with prolonged sitting and contributes importantly to lower
backache.
The "fencer's position" (one thigh and knee flexed; the other thigh
extended posteriorly with knee straight) is a common exercise specifically
designed to stretch the iliopsoas. The “cat back” (on hands and knees
the back is arched upward) is another exercise which stretches the
iliopsoas.
3.
The adductor muscles are the ones that ache a day after horseback
riding.
4.
A "pulled groin" is a sharply painful injury to the origin of the adductors,
on the pubis.
5.
A "pulled hamstring" is a similarly painful injury to the origin of the
hamstring muscles, on the ischial tuberosities.
6.
"Sartorius" comes from the Latin word meaning "tailor." To remember
its three actions, sit crossed-legged (tailor sitting).
7.
Achilles' tendon is named for Achilles, the Greek mythological hero
whose mother held him by the heel and dipped him in the river Styx when
he was a baby, to make him invincible. As an adult he died of a poisoned
arrow to the calcaneus, which didn't get dipped....
8.
The Spanish word for socks is "calcetines;" it is related to the Latin
calcaneus (heel). Peroneus longus means "long pin" in Latin. Observe
its shape.
9.
Tibialis anterior is a muscle which can be involved in painful "shin
splints.”