The skull is composed of 22 bones that aid in the support and movement, and protection of the brain. The frontal bone forms the forehead and the superior part of the eye’s orbit supporting the eyebrows. The parietal bones form the superior and lateral walls of cranium. Temporal bones lie inferior to the parietal bones and meets with the parietal bones to form the squamosal sutures. The occipital bone forms the floor and the back of the wall of the skull.
The intermediate portion or infraorbital head arises from the lower margin of the orbit immediately above the infraorbital foramen, some of its fibers being attached to the maxilla, others to the zygomatic bone. Its fibers converge, to be inserted into the muscular substance of the upper lip between the angular head and the Caninus. The lateral fibers, forming the zygomatic head, arise from the malar surface of the zygomatic bone immediately behind the zygomaticomaxillary suture and pass downward and medialward to the upper lip. Its main function is to elevate the upper lip. Effect on complete denture On maximum contraction of the Quadratus Labii superior the upper lip is pulled upward raising the upper lip dragging the labial gingivomucosal sulcus superiorly.
Permission required for reproduction or display. Mesenchymal cell Osteocyte Osteoblasts Sheet of condensing mesenchyme Trabecula Calcified bone Osteoid tissue Blood capillary Fibrous periosteum 1 Condensation of mesenchyme into soft sheet permeated with blood capillaries 2 Deposition of osteoid tissue by osteoblasts on mesenchymal surface; entrapment of first osteocytes; formation of periosteum Osteoblasts Trabeculae Osteocytes Fibrous periosteum Osteoblasts Spongy bone Marrow cavity Compact bone 3 Honeycomb of bony trabeculae formed by continued mineral deposition; creation of spongy bone 4 Surface bone filled in by bone deposition, converting spongy bone to compact bone. Persistence of spongy bone in the middle layer. Fig. 7.10-1a Copyright © The McGraw-Hill Companies, Inc.
The axial skeleton includes the skull, spinal column, ribs and sternum. The appendicular skeleton includes all upper and lower extremities, the shoulder girdle and the pelvic girdle. Bones come in four main shapes, long, short, flat and irregular and are composed of webs of collagen fibers reinforced with calcium and phosphorous. The collagen provides flexibility while the minerals provide tensile strength. The axial skeletal makes up the upper structure of the skeletal system.
Bone tissue structure Bone is hierarchically organized. Zooming in the bone structure (Fig. 4a), we find the osteons or Haversian systems, which are the basic unit of structure of compact bone. Osteons consist of concentrically arranged layers, or lamellae, of compact bone tissue, that surround a central canal, the Haversian canal, where bone’s blood supplies and nerves can be found (Fig. 4b).
List the general characteristics of vertebrates. The general characteristics of vertebrates are two unique features of vertebrates: a skull and a backbone. The skull forms a hard case for the brain. The backbone is composed of a series of skeletal segments called vertebrae (singular, vertebra), which enclose the nerve cord. 4.
Flat bones provide protection for the internal organs including the brain, heart, lungs, liver and kidneys. The flat bone is made up of two layers of compact bone with a layer of spongy bone in the middle. 3) The epiphyseal plate is located in the metaphysis of the long bones which is found between the epiphysis and diaphysis. The epiphyseal plate is made up of hyaline cartilage. The cartilage makes it possible for the diaphysis to grow in length, thus the epiphyseal plate is also known as the growth plate.
This plate is a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length but not in width. • Articular cartilage is a thin layer of hyaline cartlage covering the epiphysis where the bone forms a joint with another bone. This
THE SKELETAL SYSTEM – BONES AND JOINTS The skeleton consists of axial and appendicular components. The axial skeleton consists of the skull, vertebral column and bones of the thorax, while the appendicular skeleton consists of the pectoral girdle, pelvic girdle, and bones of the upper and lower limbs. You do not have to remember the names of all the bones of the body but you should familiarise yourself with those indicated on the diagrams below. There are different categories of bones: long bones, short bones, flat bones, sesamoid bones and irregular bones. Long bones – The major bones of the arms (humerus, radius, and ulna) and the legs (the femur, tibia, and fibula) are all long bones.
The axial skeleton consists of 80 bones and comprises the skull (facial bones and cranial bones), hyoid bone, , vertebral column, auditory ossicles and the thorax (the sternum and the rib bones form the thorax). The appendicular skeleton consists of 126 bones and comprises the shoulder girdles (the scapulae and the clavicle on each side of the bone form the shoulder girdles), the upper extremities (arms, wrists and hands), the pelvic girdle (including the coxal bones ilium, ischium and pubis) and the lower extremities (legs, ankles and feet), (Juvekar, 2013) (Holadia, 2012). There are four different categories of joints that are known as fibrous, cartilaginous, bony and synovial. Fibrous cartilage is found in the sutures of the cranium, collagen fibers reach from one bone to unify with another and bind adjacent bones