Download The Lower Extremities

The Lower
Extremities
Function of Lower Limbs
• The lower limbs carry our total body
weight when we are upright.
• Compared to the upper limbs, they
are stronger and thicker.
Attachment
• The lower limbs are attached to
the vertebrae at the coxal bones
(AKA hip bones)
• The coxal bones articulate with
the sacrum posteriorly, and
anteriorly, they are held together
with fibrocartilage.
The Coxal Bones
• Three fused bones per side of the
body
• Commonly called the “hip bones”
• Together with the sacrum and
coccyx, they form the pelvic girdle.
• Although the suture lines are hard to
find, each coxal bone is formed by
the fusion of 3 different bones:
– The ilium
– The ishium
– The pubis
The Ilium
• It is a large broad bone that forms
most of your hips.
• The upper edge is the iliac crest and
is an important anatomical
landmark.
• It connects posteriorly with the
sacrum at the sacroiliac joint.
The Ischium
• AKA the “sitdown bone”
• The most inferior portion of the coxal
bones.
• Has a rounded, rough curve that is
actually what we sit on.
• Has a small projection called the
ischial spine that is an important
landmark, esp in pregnant women.
• If the spine is too large or long, it
can interfere with the delivery during
birth.
The Pubis
• The most anterior part of the coxal
bones.
• Fuses the 2 coxal bones ateriorly at
a cartilaginous joint called the pubis
symphysis.
• This joint is flexible and in women, it
is what allows the pelvis to widen
and accommodate the developing
fetus.
The Socket
• The ilium, the ishium,
and the pubis all meet
and fuse at the socket
called the acetabulum.
• This deep socket is where the head
of the femur will attach to the pelvis.
The True v False Pelvis
• The pelvis is divided into two
major regions:
– The false pelvis = the area from
iliac crest to iliac crest.
– The true pelvis = the inferior
portion of the pelvis. This is the
area that allows a child to pass
during childbirth.
False Pelvis
True Pelvis
The Male vs the Female Pelvis
• The female has a larger pubic arch
and is more circular
• The female bones are thinner
• The female ilium flare more laterally
• The female sacrum is shorter and
less curved
Female Pelvis
Male Pelvis
The Femoral Region
• Made up of one bone, the
femur.
• Is the heaviest and strongest
bone of the human body.
• The proximal head is ball-like
and fits into the acetabulum of
the pelvis.
• The femur slants medially as it runs
downward.
• This brings the knees in line with the
body’s center of gravity.
Head
Patellar
surface
• Distally, the femur has 2 knob-like areas:
– The lateral condyle
– The medial condyle
• Both of these bones articulate with the
tibia below.
• Anteriorly, the distal femur has a smooth
patellar surface where the patella joins to
form the knee joint.
Lateral condyle
Patellar surface
Medial
condyle
The Lower Leg
• Made up of 2 bones:
– The tibia
– The fibula
• Are connected with an interosseous
membrane that hold the 2 bones
together along their length.
The Tibia
• AKA the “shin bone”
• The larger and more medial of the 2
lower leg bones.
• The proximal end has medial and
lateral condyles that articulate with
the distal part of the femur at the
knee.
Lateral
condyle
Medial
condyle
The Tibia
• The anterior surface of the tibia, the
tibial crest is the sharp edge that is
easily felt beneath the skin.
• Has a distal protrusion that forms
the inner part of the ankle called the
medial malleolus.
The Fibula
• Is thin bone that lies
lateral to the tibia.
• Has no part in forming
the knee joint.
• Has a distal protrusion
that forms the outer
part of the ankle called
the lateral malleolus.
The Foot
• Made up of 26 bones:
– 7 tarsal bones
– 5 metatarsal bones
– 14 phalanges
The foot bones are all held together
with ligaments
• Has 5 small and 2 large tarsal bones:
– The calcaneus or the “heel bone”
– The talus, sits inferior to and
articulates with the tibia
– The arch of the foot is made up the
metatarsal bones. (numbered 1 – 5,
medial to lateral)
• The toes of the foot are the
phalanges. (numbered 1 – 5, starting with the
hallux)
The End