10.3
Classification des os
Les os du système squelettique humain sont de formes, de tailles et de fonctions variées. Ils peuvent être classés en fonction de leur forme et de leu…
Le squelette humain adulte comprend généralement 206 os, qui sont principalement classés sur la base de leur forme comme longs, courts, plats et irréguliers.
Les os longs sont cylindriques et plus longs que larges. La plupart des os des membres, tels que le fémur, l’humérus et les os des doigts, sont de ce type.
En revanche, les os courts ont l’apparence d’un cube, avec des côtés à peu près égaux. Les carpiens du poignet et les tarses de la cheville sont des exemples d’os courts.
Les os sésamoïdes sont similaires aux os courts, mais sont plus arrondis et plus plats et sont intégrés dans les tendons ou les muscles. La rotule, ou rotule, est un os sésamoïde situé au niveau de l’articulation du genou.
Le troisième type est constitué d’os plats, illustrés par les omoplates, le sternum et les os du crâne. Ils sont minces et en forme de plaques, et bien qu’ils soient qualifiés de plats, ils sont généralement incurvés.
Enfin, les os de formes complexes sont classés comme des os irréguliers. Par exemple, les vertèbres et les os du visage ont des surfaces planes, des arcs et de multiples processus qui leur donnent une forme composite et irrégulière.
View the full transcript and gain access to JoVE Core videos
Q1: How many bones does the adult human skeleton contain?
The adult human skeleton typically comprises 206 bones. These bones vary in shape, size, and function throughout the body. They are classified into four major types based on their shape: long, short, flat, and irregular bones, with some classifications including sesamoid bones as a fifth category.
Q2: What are long bones and where are they found in the body?
Long bones are cylindrical structures that are longer than they are wide. Most bones in the limbs, including the femur, humerus, radius, ulna, tibia, fibula, and finger bones, are long bones. Despite their name, long bones can also be small in size, such as the phalanges in fingers and toes. They function to bear weight and support movement.
Q3: What distinguishes short bones from other bone types?
Short bones have a cube-like appearance with roughly equal sides. The carpals of the wrist and tarsals of the ankle are examples of short bones. Like long bones, they function to bear weight and support movement. Sesamoid bones are similar to short bones but are more rounded and flatter, embedded within tendons or muscles.
Q4: What is the patella and what type of bone is it?
The patella, commonly known as the kneecap, is a sesamoid bone found at the knee joint. Sesamoid bones are embedded within tendons and muscles and function to distribute force and reduce damage to the tendons. The patella is the largest sesamoid bone in humans, while smaller sesamoid bones are found in the thumb, index finger, wrist, and foot.
Q5: How are flat bones structured and what is their primary function?
Flat bones are thin and plate-like, though usually curved despite their name. Examples include the scapulae, sternum, and skull bones. Found primarily in the axial skeleton, flat bones function as protective structures and provide large areas for muscle attachment. The cranial bones, ribs, and pelvic bones are also categorized as flat bones.
Q6: What makes irregular bones different from other bone classifications?
Irregular bones have complex shapes that do not fit other classifications. The vertebrae and facial bones are examples, featuring flat surfaces, arches, and multiple processes. Vertebrae support the spinal cord and protect it from compressive forces. Many facial bones, particularly those containing sinuses, are classified as irregular bones due to their composite structure.
Q7: Why is bone classification by shape important for understanding skeletal anatomy?
Classifying bones by shape helps organize the skeletal system and relates structure to function. Long and short bones primarily bear weight and support movement in the appendicular skeleton. Flat bones protect organs and provide muscle attachment sites. Irregular bones support specialized functions like protecting the spinal cord. This classification system enables students to understand how bone structure determines its role in the skeletal system.