Week 3: Osteology of Sacrum, Coccyx & Femur Flashcards
Which bones form the sacrum?
5 sacral vertebrae fused
Describe the general shape of the dorsal and ventral surfaces of the sacrum:
- Dorsal: Convex
- Ventral: Concave superiorly/inferiorly and mediolaterally
What gross morphological features would you expect to see when comparing a juvenile and adult sacrum?
- In childhood the sacral vertebrae are connected by cartilage
- In the adult may see bony ridges, the transverse ridges at the sites of the cartilages, may see remnants of cartilage between S1 and S2
Where in the pelvis is the sacrum located?
Situated in the upper posterior part of the pelvic cavity
With what bone does the base of the sacrum articulate and what is found between these two bony surfaces?
Body of L5; separated from the sacrum by the L5-S1 intervertebral disc
With what bone does the apex of the sacrum articulate?
Coccyx
What structures pass through the dorsal and ventral sacral foramina?
- Ventral rami S1-S4 through the ventral foramina
- Dorsal rami of S1-S4 through the dorsal foramina
What structure is contained within the sacral canal?
Cauda equina
What are the 4 principal functions of the sacrum?
- Supports the lumbar spine
- Part of the pelvic girdle - wedged between the two iliac bones
- Transmits forces from the vertebral column sideways into the pelvis
- Forms the posterior wall of the pelvis
What is the coccyx formed from?
The coccyx is a small triangular bone formed by the fusion of 3 to 5 rudimentary vertebrae
- The first coccygeal vertebra may remain unfused and articulates with the lower end of the sacrum with intervening fibrocartilage
How is the coccyx positioned?
It is directed forwards and downwards from the sacrum so that its pelvic surface faces upwards and forwards
Which 2 muscles attach to the coccyx?
- Gluteus maximus
- Pelvic floor muscles
What are the principal functions of the lower limb?
- Bear the entire body weight (single limb stance) during locomotion
- Serve as a platform so the trunk, head, and upper limbs are based and held steady during bilateral stance
- Therefore, stability is a crucial factor at all joints
What is the function of the neck of the femur?
Facilitates movement of the hip joint, enabling the limb to swing clear of the pelvis
What is the principal structure that runs through the nutrient foramen of the femur?
Nutrient artery
What are the relations of the fascia lata and intermuscular septa to the bony features of the femur?
- The intermuscular septa are continuous, inward extensions of the fascia lata, that attach to the length of the linea aspera
- The LATERAL intermuscular septum lies between vastus lateralis and the lateral hamstring muscle (biceps femoris) and extends from the attachment of gluteus medius to the lateral condyle
- The MEDIAL intermuscular septum lies between vastus medialis and the adductors, and down the medial supracondylar line
