|
The ectodermis is responsible for the production of much of the sense organs, nervous system, and surface skin (among other things), while the endoderm contributes to the growth of structures such as the stomach and intestines, the lungs, endocrine glands, and the digestive glands. The middle layer is used to build muscular, skeleton, excretory, and reproductive systems. The mesoderm thus allows animals to become more organized in their structure (Figure 10-11b). Cnidarians, for example, are organized mainly at the level of tissues, while those with three layers possess organs and elaborate organ systems. The body plan for the advance organisms is essentially tube-within-a-tube with the gut cavity inside the body cavity (the coelom). In our body the coelom is divided by the diaphragm and membranes into the
|
Figure 10-11b Cellular Differentiation |
peritoneal cavity (contains intestines and reproductive organs), pleural cavities (contain lungs), and pericardial cavity (contains heart).
|
|
|
All the vital body organs except for the brain are enclosed within the trunk or torso. The trunk contains two large cavities separated by a muscular sheet called the diaphragm. The upper cavity, known as the thorax or chest cavity, contains the heart and lungs. The lower cavity, called the abdominal cavity, contains the stomach, intestines, liver, and pancreas, which all play a role in digesting food. Also within the trunk are the kidneys and bladder, which are part of the urinary system, and the reproductive organs, which hold the seeds of new human life. Figure 10-12a depicts the front view of the body cavity; while Figure 10-12b shows some inner organs. The three kinds of germ layers have differentiated into more than 350 different kinds of tissues and organs in adults. Table 10-01 is a list of the human organ systems, together with its function, and major
|
|
|
components. All body systems work together; none are independent.
|
Organ System |
Functions |
Components |
Circulatory |
Transports nutrients, gases (O2, CO2), hormones and wastes through the body |
Heart, blood vessels and blood |
Digestive |
Breakdowns and absorbs nutrients for growth and maintenance |
Mouth, esophagus, stomach, liver, pancreas, gallbladder, small and large intestines |
Endocrine (Hormonal) |
Relays chemical messages through the body for controlling physiological processes |
Hypothalamus, pineal, pituitary, thyroid, thymus, pancreas and adrenal glands |
Excretory |
Filters out cellular wastes, toxins and excess water or nutrients from the circulatory system |
Kidneys, ureters, bladder, urethra, lungs, sweat pores, and intestine |
Immune |
Destroys or removes invading microbes, viruses; the lymphatic system also removes fat, and excess fluids from the blood. Skin is the outermost defense against pathogens |
Spleen, thymus, bone marrow, lymph, lymph nodes and vessels, white blood cells, T- and B- cells, skin |
Musculo-skeletal |
Supports and moves organism; also protects delicate internal organs and provides attachment sites for the organs. |
Skeletal and smooth muscles; bones, cartilage, tendons, and ligaments |
Nervous & sensory |
Relays electrical signals, directs movement, controls physiological processes, and responses to environment |
Brain, nervous system, and the five senses |
Reproductive |
manufactures cells for reproduction |
Female: ovaries, oviducts, uterus, vagina, and mammary glands; male: testes, as deferens, seminal vesicles, penis, and prostate gland |
Respiratory |
Provides gas exchange between the blood and the environment |
Nose, trachea, and lungs |