ANAT20006 Lecture Notes - Lecture 18: Lesser Trochanter, Tuberosity Of The Tibia, Interosseous Membrane
12 Jun 2018
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LECTURE 18
LOWER LIMBS (1) BONES & JOINTS
•Girdle attaching lower limb to axial skeleton.
•Lower limb: thigh, leg, foot. Generally, the organisation of the lower limb is common through
evolution, just with adaptations on how we use the structures creating differences.
•Thigh: single long bone, connects to leg with 2 long bones (this is same as arm) then tarsal bones
then digits.
LOWER LIMB BONES & JOINTS
•(1) Shoulder girdle made for mobility. Our pelvic girdle, however, is made for stability. It carries
our whole body weight. Lower limb bones tend to be longer; increase leverage, stronger.
•These limbs rotate during development. At 4-5 weeks of age, the upper limbs begin to develop
(bud out) in the embryo. As this happens, it rotates in a lateral orientation (outwards), bringing
the flexor surfaces anteriorly. Few weeks later our lower limbs begin to bud out and rotate
medially (inwards), bringing our lower limb flexor surfaces
posteriorly.
•Cats and dogs don’t have angulated femurs. We have them so
that our centre of gravity remains underneath our pelvis.
•Adaptation over evolutionary times; lost ability to use big
toe. However they can be, if required, remarkably dextrous.
PELVIC GIRDLE
•(2) distal component of axial skeleton is the
sacrum. 5 sacral bones/vertebra which fuse
during development, ultimately for increased
stability. We have head, upper limbs, thoracic
cage and abdomen weight has to be transferred
via skeleton to sacrum and pelvic girdle. It is thus
more stable to have 1 large sacral bone than 5 little ones.
•Sacrum articulates with hip bone. We have 2 hip bones, one on each
the RHS and LHS. These arch anteriorly and meet in the midline at the
front, generating a stable bony ring.
•Pelvis is the most sexually dimorphic bone in the body. Male pelvis is
more narrow and higher, female is relatively wider and more shallow.
•Each hip bone has 3 distinct bones that develop independently and fuse
late in development. KNOW THESE 3 COMPONENTS:
•Ilium: big bony ridges (when you put your hands on your hips you
are touching the ilium).
•Ischium: what you sit on.
•Pubis: (pubic bone).
•These 3 bones come together at a point called
the acetabulum. This is also where the lower
limb articulates with the pelvis. Known
colloquially as a hip joint even though it isn’t really.
FEMUR
•(3) long bone of thigh. Recall the humerus. Single long bone with a
head, a neck. We also have trochanters (comparable to tuberosities in
humerus). There is a greater trochanter and lesser trochanter.
•There is also a long shaft, terminating in medial particular condyle
and lateral articular condyle. The patella articulates with the femur. It is
sesamoid bone and has leverage for knee extensors.
Lecture 18 - Friday 1 September 2017
ANAT20006 - HUMAN STRUCTURE & FUNCTION
2
2
THE NECK
•(4) Very important. In a standing position
with weight bearing, weight is transferred
to superior aspect of acetabulum and then
superior aspect of head of the femur.
•Bony trabeculae line up against forces of
weight bearing, and also where muscles attach
to and pull on bones.
TIBIA & FIBULA
•(5) Femur articulates with 2 leg long bones, tibia and fibia.
•Tibia: long bone, weight bearing, bears all body weight down to
angle. Is flat and has a plateau anteriorly. Trochlear notch for
ankle joint.
•Has a shaft which is in the subcutaneous part. The tibial
tuberosity just below the knew in front of tibia, distal to
patella. Tibia terminates in the medial malleolus, which is the
bump on the side of the angle.
•Fibula: long bone. not weight bearing. Joins the tibia via
interosseus membrane. Shaft for muscle attachments, and lateral
malleolus.
•Just like how in the arm the radius and ulna move relative to
each other; we can pronate and supinate. Our tibia and fibula
DO NOT do this, due to the interosseus membrane.
THE ANKLE & FOOT
•(6) distal to leg bones are foot bones. Same
general arrangement as hand larger &
heavier for weight transfer.
•Same organisation as hand
bones but carpals become
tarsals here. Don’t need to
know the 7 names of them,
just remember these 2:
•Talus: forms ankle bone, and under talus we have
calcaneus.
•Tarsal bones
articulate with
metatarsals, which in
turn articulate with
phalanges.
THE LINE OF GRAVITY
•(7) effect of gravity on joints. We don’t
want line of gravity going directly through
hip ankle or knee joints. See the line of
gravity passes sightly behind the hip joint and
slightly in front of the knee joint.
•passes behind hip joint
•(resisted by anterior capsule)
•slightly in front of knee
•(resisted by posterior capsule)
•long way in front of ankle
•(resisted by calf muscles, especially soleus)
Lecture 18 - Friday 1 September 2017
ANAT20006 - HUMAN STRUCTURE & FUNCTION
6
Medial view
Document Summary
Lower limbs (1) bones & joints: girdle attaching lower limb to axial skeleton, lower limb: thigh, leg, foot. Lower limb bones & joints: (1) shoulder girdle made for mobility. Our pelvic girdle, however, is made for stability. Lower limb bones tend to be longer increase leverage, stronger: these limbs rotate during development. At 4-5 weeks of age, the upper limbs begin to develop (bud out) in the embryo. As this happens, it rotates in a lateral orientation (outwards), bringing the flexor surfaces anteriorly. Few weeks later our lower limbs begin to bud out and rotate medially (inwards), bringing our lower limb flexor surfaces posteriorly: pubis: (pubic bone), these 3 bones come together at a point called the acetabulum. This is also where the lower limb articulates with the pelvis. Known colloquially as a hip joint even though it isn(cid:282)t really. Single long bone with a head, a neck. We also have trochanters (comparable to tuberosities in humerus).
