chapter 5 Flashcards
Differentiate between bones, ligaments, and cartilage.
Most of the mass of bones consists of nonliving extracellular crystals of calcium minerals that give bones their hard, rigid appearance and feel. But bone is actually a living tissue that contains several types of living cells involved in bone formation and remodeling, plus nerves and blood vessels. Indeed, bones bleed when cut during orthopedic surgery or when they break.
Ligaments attach bone to bone. Ligaments consist of dense fibrous connective tissue, meaning that they are a regular array of closely packed collagen fibers all oriented in the same direction, with just a few fibroblasts in between. (Recall that fibroblasts are cells that produce and secrete the proteins that compose collagen, elastic, and reticular fibers.) Ligaments confer strength to certain joints while still permitting movement of the bones in relation to each other.
Cartilage contains fibers of collagen and/or elastin in a ground substance of water and other materials. Cartilage, smoother and more flexible than bone, is found where support under pressure is needed and movement is necessary. There are three types of cartilage in the human skeleton. Fibrocartilage consists primarily of collagen fibers arranged in thick bundles. It withstands both pressure and tension well. The intervertebral disks between the vertebrae, and also certain disklike supportive structures in the knee joint called menisci, are made of fibrocartilage. Hyaline cartilage is a smooth, almost glassy cartilage of thin collagen fibers. Hyaline cartilage forms the embryonic structures that later become the bones. It also covers the ends of mature bones in joints, creating a smooth, low-friction surface. Elastic cartilage is mostly elastin fibers, so it is highly flexible. It lends structure to the outer ear and to the epiglottis, a flap of tissue that covers the larynx during swallowing.
Describe the five functions of bones.
Bones perform five important functions. The first three—support, protection, and movement—are the same as the functions of the skeleton overall, which is, after all, primarily bone. The rigid support structure of bones allows us to sit and to stand upright. The bones of the skeleton also support, surround, and protect many of our soft internal organs, such as the lungs, liver, and spleen. The attachment of bones to muscles makes it possible for our bodies to move. The fourth and fifth functions of bones—blood cell formation and mineral storage—are harder to remember, but they are just as important. Cells in certain bones are the only source of new red and white blood cells and platelets for blood. Without this ability to produce new blood cells, we would die within months. Bones also serve as an important long-term storage depot for two minerals, calcium and phosphate, that can be drawn from bone when necessary (for example, during pregnancy to support the growth of a fetus).
Differentiate between compact and spongy bone
Dense compact bone forms the shaft and covers each end, and less dense spongy bone fills the inner regions of the epiphyses.
Differentiate between yellow and red bone marrow
. A central cavity in the diaphysis is filled with yellow bone marrow. Yellow bone marrow is primarily fat that can be utilized for energy. In certain long bones, most notably the long bones of the upper arms and legs (humerus and femur, respectively), the spaces within spongy bone are filled with red bone marrow. Special cells called stem cells in the red bone marrow produce red and white blood cells and platelets.
Identify the epiphysis and diaphysis of a long bone
A typical long bone, so called because it is longer than it is wide, consists of a cylindrical shaft (called the diaphysis) with an enlarged knob called an epiphysis at each end (Figure 5.1a).
Describe how osteocytes in compact bone are arranged in osteons
Taking an even closer look at compact bone (Figure 5.1c), we see that it is made up largely of extracellular deposits of calcium phosphate enclosing and surrounding living cells called osteocytes (from the Greek words for “bone” and “cells”). Osteocytes are arranged in rings in cylindrical structures called osteons (sometimes called Haversian systems). Osteocytes nearest the center of an osteon receive nutrients by diffusion from blood vessels that pass through a central canal (Haversian canal).
What is the function of a central canal?
In bone, the hollow central tube of an osteon that contains nerves and blood vessels. Waste products produced by the osteocytes are exchanged in the opposite direction and are removed from the bone by blood vessels.
Describe the function of ligaments
Ligaments attach bone to bone. Ligaments consist of dense fibrous connective tissue, meaning that they are a regular array of closely packed collagen fibers all oriented in the same direction, with just a few fibroblasts in between. (Recall that fibroblasts are cells that produce and secrete the proteins that compose collagen, elastic, and reticular fibers.) Ligaments confer strength to certain joints while still permitting movement of the bones in relation to each other.
What type of connective tissue are ligaments composed of?
Fibrous collagen fibers
What type of protein fiber makes up much of ligaments
collagen
Summarize in what way cartilage differs from bone.
. Cartilage contains fibers of collagen and/or elastin in a ground substance of water and other materials. Cartilage, smoother and more flexible than bone, is found where support under pressure is needed and movement is necessary There are three types of cartilage in the human skeleton. Fibrocartilage consists primarily of collagen fibers arranged in thick bundles. It withstands both pressure and tension well. The intervertebral disks between the vertebrae, and also certain disklike supportive structures in the knee joint called menisci, are made of fibrocartilage. Hyaline cartilage is a smooth, almost glassy cartilage of thin collagen fibers. Hyaline cartilage forms the embryonic structures that later become the bones. It also covers the ends of mature bones in joints, creating a smooth, low-friction surface. Elastic cartilage is mostly elastin fibers, so it is highly flexible. It lends structure to the outer ear and to the epiglottis, a flap of tissue that covers the larynx during swallowing.
What type of cartilage form the model structure that later turns into bone?
Hyaline cartilage
What type of cells form cartilage?
In the earliest stages of fetal development, the rudimentary models of future bones are created out of hyaline cartilage (Figure 5.2a) by cartilage-forming cells called chondroblasts. Most chondroblasts are short-lived, however; within 2–3 months they begin to die, and as they do the cartilage dissolves, making room for blood vessels (Figure 5.2b).
What type of cells form bone?
At the same time, the periosteum begins to form on the outer surface of the developing bone. The blood vessels carry bone-forming cells called osteoblasts (from the Greek words for “bone” and “to build”) into the area from the developing periosteum. Osteoblasts secrete a mixture of proteins (including collagen) called osteoid, which forms a matrix that provides internal structure and strength to bone (Figure 5.2c). Osteoblasts also secrete enzymes that facilitate the crystallization of hard mineral salts of calcium phosphate around and between the osteoid matrix. As more and more calcium phosphate is deposited, the osteoblasts become embedded in the hardening bone tissue. In mature compact bone, approximately one-third of the structure is osteoid and two-thirds is crystals of calcium phosphate.
Which of these cell types eventually becomes an osteocyte when it becomes trapped in bone.
Osteoblast
