<< Chapter < Page Chapter >> Page >

The sacral promontory    is the anterior lip of the superior base of the sacrum. Lateral to this is the roughened auricular surface, which joins with the ilium portion of the hipbone to form the immobile sacroiliac joints of the pelvis. Passing inferiorly through the sacrum is a bony tunnel called the sacral canal    , which terminates at the sacral hiatus    near the inferior tip of the sacrum. The anterior and posterior surfaces of the sacrum have a series of paired openings called sacral foramina    (singular = foramen) that connect to the sacral canal. Each of these openings is called a posterior (dorsal) sacral foramen    or anterior (ventral) sacral foramen    . These openings allow for the anterior and posterior branches of the sacral spinal nerves to exit the sacrum. The superior articular process of the sacrum    , one of which is found on either side of the superior opening of the sacral canal, articulates with the inferior articular processes from the L5 vertebra.

The coccyx, or tailbone, is derived from the fusion of four very small coccygeal vertebrae (see [link] ). It articulates with the inferior tip of the sacrum. It is not weight bearing in the standing position, but may receive some body weight when sitting.

Sacrum and coccyx

This figure shows the structure of the sacrum and coccyx. The left panel shows the vertebral column with the sacrum and coccyx highlighted in pink. The middle panel shows the anterior view and the right panel shows the posterior view of the sacrum and coccyx.
The sacrum is formed from the fusion of five sacral vertebrae, whose lines of fusion are indicated by the transverse ridges. The fused spinous processes form the median sacral crest, while the lateral sacral crest arises from the fused transverse processes. The coccyx is formed by the fusion of four small coccygeal vertebrae.

Intervertebral discs and ligaments of the vertebral column

The bodies of adjacent vertebrae are strongly anchored to each other by an intervertebral disc. This structure provides padding between the bones during weight bearing, and because it can change shape, also allows for movement between the vertebrae. Although the total amount of movement available between any two adjacent vertebrae is small, when these movements are summed together along the entire length of the vertebral column, large body movements can be produced. Ligaments that extend along the length of the vertebral column also contribute to its overall support and stability.

Intervertebral disc

An intervertebral disc    is a fibrocartilaginous pad that fills the gap between adjacent vertebral bodies (see [link] ). Each disc is anchored to the bodies of its adjacent vertebrae, thus strongly uniting these. The discs also provide padding between vertebrae during weight bearing. Because of this, intervertebral discs are thin in the cervical region and thickest in the lumbar region, which carries the most body weight. In total, the intervertebral discs account for approximately 25 percent of your body height between the top of the pelvis and the base of the skull. Intervertebral discs are also flexible and can change shape to allow for movements of the vertebral column.

Each intervertebral disc consists of two parts. The anulus fibrosus    is the tough, fibrous outer layer of the disc. It forms a circle (anulus = “ring” or “circle”) and is firmly anchored to the outer margins of the adjacent vertebral bodies. Inside is the nucleus pulposus    , consisting of a softer, more gel-like material. It has a high water content that serves to resist compression and thus is important for weight bearing. With increasing age, the water content of the nucleus pulposus gradually declines. This causes the disc to become thinner, decreasing total body height somewhat, and reduces the flexibility and range of motion of the disc, making bending more difficult.

Questions & Answers

how many classes of drugs do we have?
Jesse Reply
site of fracture in the kneel
holuwahseun Reply
what is pelvis
Aisha Reply
Complex of bones that connect the trunk and the legs,supports and balance the trunk.
Orpha
What is d most heaviest organ in d body
Abraham Reply
Liver
Akasi
The skin
Akasi
skin
Divya
why skin?
Sam
liver
Anne
water
Mehdi
Heart
Biplob
the brain
lehumo
skin
Emma
skin
jessica
largest internal organ is the liver
jessica
liver is the heaviest organ
Eyyammeh
the liver is the heaviest organs
Khh
What is the meaning? What does it entails to? What are the works of Arthropologists?
Orpha Reply
bones of appendicular skeleton
hemalatha Reply
Fore limbs, hind limbs, pectoral and pelvic girdle
Abraham
Functions of the thoracic cage
Fereh Reply
protect all the organs and tissues from any impact or injury
Javier
It protects the heart other tissues in the chest region
Abraham
why sickle cell carrier people don't get malaria
Boakye Reply
Bcos mosquitoes are not attracted by their blood due to poor oxygen
Abraham
What is the amniotic fluid
bollywood Reply
amniotic fluid is the fluid that is inside the uterus with the baby.
Fati
shielded
Varun
This fluid serves as a cushion for the growing fetus but also serves to facilitate the exchange of nutrients, water, and biochemical products between mother and fetus.
Anne
it also reduces friction during birth as it wets the birth canal during delivery
steve
Amniotic fluid can be taken out by inserting needle to detect birth abnormalities as the foetus cells are present in amniotic fluid. This process is known as amniocentesis.
Biplav
structure of heart and it's function (10 mark )
Priyanka Reply
not possible
Abraham
What is the best book on physiology?
cesar Reply
describe varicocele
malulu
what do you mean by peritoneum
Siba Reply
It is thick covering surrounding the abdomen
Awais
r8
how to become good in Anatomy and physiology
malulu
hi
Milkah
hlo
Wani
What are is the last solution to abdomen pain in pregnant women
Umoru
no it is in kidney
Tantray
Kk
Umoru
structure of heart and it's function
Priyanka
Serous membrane lining the cavity of the abdomen
bollywood
it is four lobs structure and it is triangular in shaped. it 's function pumping the blood
ABDULLAH
explain root of lungs
ABDULLAH
Glomerular pressure -capsule pressure -colloid osmosis pressure
malulu Reply
how to describe mechanism of micturition
malulu
spleen is important?
AKASH Reply
helpful in destruction of rbc
It is imp in storing blood and destruction of microbes and harmful particles
Awais
ty sir
AKASH
K
Umoru
what are the sources of glucose in the body
malulu
describe mechanism of micturition
malulu
Pancreatic hormones with function
mami Reply
Insulin, which helps to regulate our blood sugar levels.
Bb
glucagon which is antagonistic to insulin increase the blood glucose level,. Somatostatin help to regulate the levels of both insulin and glucagon
Ashish
thnks for helping
nimco
thanks
Narendra
what is a lymph node.?
AKASH
lymph nodes are small kidney shaped organs of the lymphatic system.
Trishauna
there are several hundred lymph nodes found mostly throughout the thorax and abdomen of the body with the highest concentrations in the auxiliary (armpit) and inguinal groin regions.
Trishauna

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask