49.1 The bodies of vertebrates are organized into functional systems Organization of the bod Brain Spinal cord The bodies of all mammals have the same general archi Vertebrae tecture(figure 49.2), and are Peritoneal body plan of other vertebrate groups. This body plan is basically a tube suspended within a tube. Starting from the inside, it is composed of the digestive tract, a lor be that travels from one end of the body to the other mouth to anus). This tube is suspended within an inter- pleural cavtiy nal body cavity, the coelom. In fishes, amphibians, and most reptiles, the coelom is subdivided into two cavities Thoracic one housing the heart and the other the liver stomach and intestines. In mammals and some reptiles, a sheet of muscle, the diaphragm, separates the peritoneal cavity, which contains the stomach, intestines, and liver, from the thoracic cavity; the thoracic cavity is further subdi FIGURE 49.2 Architecture of the vertebrate body. All vertebrates have a vided into the pericardial cavity, which contains the heart, dorsal central nervous system. In mammals and some reptiles, a ind pleural cavities, which contain the lungs. All verte muscular diaphragm divides the coelom into the thoracic cavity brate bodies are supported by an internal skeleton made and the peritoneal cavity of jointed bones or cartilage blocks that grow as the body grows. A b skull surrounds the brain and a col Epithelial Nerve tissue Connective umn of bones. the vertebrae. sur sue rounds the dorsal nerve cord, or spin There are four levels of organizatie in the vertebrate body:(1)cells,(2)tis sues,()organs, and (4)organ systems Like those of all animals. the bodies of Stratified epithelium vertebrates are composed of different ell types. In adult vertebrates, there ning stomepithelium are between 50 and several hundred different kinds of cells ssues Groups of cells similar in structure and ol function are organized into tissues. Early in development, the cells of the Cuboidal epithelium growing embryo differentiate(special kidney tubules ize)into three fundamental embryonic Muscle Tissues tissues,called germ layers. From inner most to outermost layers, these are the endoderm. mesoderm, and ecto derm. These germ layers, in turn, dif- ferentiate into the scores of different cell types and tissues that are character istic of the vertebrate body In adult vertebrates, there are four principal Smooth muscle in intestinal wall voluntary muscles hear c muscle in kinds of tissues, or primary tissues: ep- helial, connective, muscle, and nerve FIGURE 49.3 (figure 49.3), each discussed in separate vertebrate tissue types. Epithelial tissues are indicated by blue arrows, connective tissues sections of this chapter. by green arrows, muscle tissues by red arrows, and nerve tissue by a yellow arrow 984 Part XIlI Animal Form and Function984 Part XIII Animal Form and Function Organization of the Body The bodies of all mammals have the same general archi￾tecture (figure 49.2), and are very similar to the general body plan of other vertebrate groups. This body plan is basically a tube suspended within a tube. Starting from the inside, it is composed of the digestive tract, a long tube that travels from one end of the body to the other (mouth to anus). This tube is suspended within an inter￾nal body cavity, the coelom. In fishes, amphibians, and most reptiles, the coelom is subdivided into two cavities, one housing the heart and the other the liver stomach, and intestines. In mammals and some reptiles, a sheet of muscle, the diaphragm, separates the peritoneal cavity, which contains the stomach, intestines, and liver, from the thoracic cavity; the thoracic cavity is further subdi￾vided into the pericardial cavity, which contains the heart, and pleural cavities, which contain the lungs. All verte￾brate bodies are supported by an internal skeleton made of jointed bones or cartilage blocks that grow as the body grows. A bony skull surrounds the brain, and a col￾umn of bones, the vertebrae, sur￾rounds the dorsal nerve cord, or spinal cord. There are four levels of organization in the vertebrate body: (1) cells, (2) tis￾sues, (3) organs, and (4) organ systems. Like those of all animals, the bodies of vertebrates are composed of different cell types. In adult vertebrates, there are between 50 and several hundred different kinds of cells. Tissues Groups of cells similar in structure and function are organized into tissues. Early in development, the cells of the growing embryo differentiate (special￾ize) into three fundamental embryonic tissues, called germ layers. From inner￾most to outermost layers, these are the endoderm, mesoderm, and ecto￾derm. These germ layers, in turn, dif￾ferentiate into the scores of different cell types and tissues that are character￾istic of the vertebrate body. In adult vertebrates, there are four principal kinds of tissues, or primary tissues: ep￾ithelial, connective, muscle, and nerve (figure 49.3), each discussed in separate sections of this chapter. 49.1 The bodies of vertebrates are organized into functional systems. Cranial cavity Brain Thoracic cavity Diaphragm Peritoneal cavity Vertebrae Spinal cord Pericardial cavity Right pleural cavtiy FIGURE 49.2 Architecture of the vertebrate body. All vertebrates have a dorsal central nervous system. In mammals and some reptiles, a muscular diaphragm divides the coelom into the thoracic cavity and the peritoneal cavity. Epithelial Tissues Bone Blood Loose connective tissue Muscle Tissues Smooth muscle in intestinal wall Cuboidal epithelium in kidney tubules Columnar epithelium lining stomach Stratified epithelium in epidermis Skeletal muscle in voluntary muscles Cardiac muscle in heart Nerve Tissue Connective Tissues FIGURE 49.3 Vertebrate tissue types. Epithelial tissues are indicated by blue arrows, connective tissues by green arrows, muscle tissues by red arrows, and nerve tissue by a yellow arrow