Human Body Systems and Functions: A Detailed Look
Circulatory System
The circulatory system is a set of the cardiovascular and lymphatic systems.
Locomotor System
The locomotor system is a group of the skeletal system, joints, and muscles. These systems, coordinated by the nervous system, allow locomotion.
Reproductive System
The reproductive system consists of the sex organs (male and female).
Respiratory System
The respiratory system includes the organs used for respiration, primarily the lungs, within which we can find the bronchioles and cilia.
Urinary System
The urinary system is responsible for eliminating waste from the body through urine.
Digestive System
The digestive system is responsible for processing food and includes the mouth, esophagus, stomach, intestines, and attached glands.
Chewing and Swallowing
In carrying out chewing, the mouth produces an abundant secretion of saliva. This is due to a congenital reflex action or unconditional reflex. The secretion of saliva is a direct response to stimulation of taste cells or the oral mucosa.
The secretion of saliva can also be produced in other ways. The mouth “waters” at the sight or smell of food, and even at the mere thought of food, especially when we are hungry. The experiments of Pavlov showed that in the animal kingdom, there is also a relationship between abstract concepts and salivary secretion learned behaviors.
Saliva
Indeed, although there were no ptyalin in saliva, this does not pose great harm to the body. In the small intestine, other, usually more powerful, juices take over the digestion of carbohydrates. In practice, they do not take into account the work done by the ptyalin and are capable of breaking down larger molecules into smaller, directly absorbed units. Saliva serves primarily to “wet” food, making it workable and easier to swallow. It also keeps the mouth clean, preventing the remaining food particles between teeth and other cavities. Saliva also plays a key role in the production of voice.
Chewing
During mastication, lips, jaw, cheeks, and the tongue work with a remarkable coordination of movements. Incisor teeth penetrate food and hold it, while hands pull it to rip. The mission to grind is reserved for the molars. The jaws also have the ability to close with dramatic force and carry out lateral movements that help to grind food increasingly fine.
Swallowing
Swallowing is a very complicated process. The food, in fact, to move from the mouth to the esophagus, must pass through the pharynx, where other pathways converge: the nasal cavities, larynx, esophagus, and oral cavity. The pharynx is thus the intersection of two major lines of passage: the first carries air, ranging from the inner part of the nasal cavities to the larynx and, hence, to the lungs; the other, through which food passes, runs from the mouth to the esophagus.
Phases of Swallowing
- The first phase of swallowing, during which food passes from the back of the tongue to the isthmus of fauces, is controlled by the will. The stages during which food passes through the pharynx take place automatically.
- The soft palate rises, closing the hole that connects the nasal cavity with the pharynx, preventing air from entering and dragging the food into the larynx.
- The latter is then closed in due course by the simultaneous descent of the epiglottis and laryngeal elevation so that the bolus is left with no option but to choose the only way that remains open, that is, which leads to the esophagus.
- Once in contact with the muscular walls of the esophageal channel, the bolus causes a peristaltic wave of contraction that travels through the tube along its length, taking the food forward until the valve closes the upper entrance of the stomach, called the cardia.
Dental Enamel
Dental enamel is a tissue made up of hydroxyapatite and protein (in a low ratio). It is the hardest tissue in the human body. In areas where the glaze is thinner or has worn away, it can be extremely sensitive. The enamel is translucent and impervious to pain because it has no nerve endings. With fluorine, fluorhydroxyapatite crystals form that are much stronger than hydroxyapatite against dental caries.
Dentin
Dentin is a mineralized tissue, but to a lesser degree than enamel. It is responsible for the color of teeth. It contains tubules where odontoblasts project. Dentin provides elasticity to the fragile but hard enamel.
Dental Cement
Dental cement is a highly specialized connective tissue. It is a hard, opaque, yellowish layer lining the dentin at the root of the tooth. It connects the tooth with the rest of the mandible or maxilla.
Dental Pulp
Dental pulp is a mesodermal tissue composed of a soft tissue containing blood vessels (arteries and veins) that carry blood to the tooth and nerve fibers that provide sensation to the tooth. These nerves pierce the root (tooth) through thin channels. Its main cells are the odontoblasts (cells of both pulp and dentin); they produce dentin and maintain the vitality of dentin. The odontoblasts have extensions known as Tomes’ processes, staying in the dentinal tubules.
Digestion
Digestion is the process of transforming food previously ingested into simpler substances to be absorbed. Digestion occurs in multicellular organisms and in cells at a subcellular level. This process involves different types of enzymes. The digestive system is very important in digestion because heterotrophic organisms depend on external sources of raw materials and energy for growth, maintenance, and operation. Food is used to generate and repair tissues and produce energy. Autotrophic organisms (plants, photosynthetic organisms), however, capture light energy and transform it into chemical energy, usable by animals.
Mechanics of Breathing in Humans
The membrane through which air and blood have to establish their changes is the wall of the pulmonary vesicles. The blood comes to it, under circulatory function, by the capillaries of the lung. For air to get to these vesicles, we need a series of acts by the lung mechanics and chest.
The air enters the lungs under a phenomenon called inspiration and leaves the lungs through the act of exhalation.[1]
Inspiration
Inspiration or inhalation is the process by which air enters from an external medium into an organism (lungs). Communication from the lungs to the outside is made through the trachea.
Expiration
Exhalation or expiration is the opposite of inspiration, during which the air from the lungs exits. It is a passive phase of breathing because the chest retracts and all diameters decrease without intervention by muscular contraction, returning the chest to its primitive form. The muscles brought into play to expand the chest relax at this stage, the ribs return to their initial position, and the diaphragm relaxes.