Human Biology: Nutrition, Cells, Tissues, Health, and Disease
Nutrition
Nutrition involves incorporating environmental matter and energy into cells to reproduce, replace damaged structures, and move. Waste products are urine and CO2. The following systems are involved: digestive, respiratory, circulatory, and excretory. Nutrition is not the same as digestion.
Organic Molecules
Organic molecules are made of atoms of carbon, oxygen, nitrogen, and phosphorus, and some contain sulfur. They can be very large and complex.
Inorganic Molecules
Inorganic molecules are much smaller and simpler.
Cells
The cell is the simplest unit equipped with its own life and able to perform the three vital functions. A set of cells forms tissues.
Types of Cells
- Prokaryotic: These are very small and simple, with no defined nucleus. Their genetic material is directly scattered throughout the cytoplasm. The only organelles they contain are ribosomes.
- Eukaryotic: These are very large and complex. Their genetic material is protected by a membrane, forming a true nucleus. They also have many organelles, such as:
- Plasma membrane: Its mission is to limit the cell’s contents.
- Nucleus: This is surrounded by a membrane with pores. Inside is the DNA, and it serves as the control center of the cell.
- Mitochondria: These are the power plants of cells, as they perform cellular respiration. This process breaks the bonds of organic matter.
- Golgi apparatus: Its mission is to produce certain substances and package them inside vesicles.
- Ribosomes: These are responsible for the synthesis of proteins.
- Smooth endoplasmic reticulum: In charge of the production of certain lipids.
- Rough endoplasmic reticulum: Transportation and storage of proteins synthesized by ribosomes.
Tissues
A tissue is a set of specialized cells with a defined structure.
Types of Tissues
- Epithelial: Found in the dermis of the skin, blood vessels, digestive tract, and airways. Its cells are very close to one another without intercellular substance. The main function is to coat and protect the exterior of the body and internal cavities.
- Connective: Located on the outside of the organs (surrounding them), in tendons and ligaments, in the dermis, and in bone marrow. It is rich in intercellular substance composed of two types of fibers: collagen and elastin. Its main functions are to connect organs and join bones to each other and bones to muscles.
- Adipose: Located under the skin and around certain organs. It is composed of rounded cells that accumulate fat. Its functions are energy reserve, thermal insulation, and protection against shocks.
- Cartilaginous: Located in the ears, tip of the nose, rings of the trachea, joints, and intervertebral discs. It is composed of intercellular substance rich in elastic and collagen fibers. Its functions are to provide consistency to areas where it is found and to facilitate the movement of bones.
- Bone: Also found in bones. It is formed by intercellular substance (solid), and its main functions are to support the body, attach muscles, and protect some organs.
- Muscle: There are three types: striated skeletal muscle (located in voluntary movement muscles), smooth muscle (found in involuntary action muscles), and cardiac striated muscle (found in the heart). It is formed by muscle fibers, and its function is to contract and relax, allowing body movement.
- Nervous: Located in the brain. It is composed of neurons, and its mission is to transmit nerve impulses from receptors to nerve centers.
Health
Health is the state of complete physical, psychological, and social well-being, not just the absence of disease.
Determinants of Health
- Biological: These are typical of human nature, with which the individual is born. They can be passed from parents to children.
- Environment: An unhealthy environment includes water and air pollution, waste, noise, poison, poverty, and ignorance.
- Lifestyle Habits: These are ways of life that people learn from a young age. Lifestyle habits can be modified to achieve good health.
- Healthcare: Impacts health in two ways: in terms of prevention and in the solution of diseases.
Types of Diseases
- Congenital: Present at birth.
- Acquired: Appear throughout life. These can be:
- Produced by living beings
- Produced by physical mechanisms or atmospheric agents
- Produced by chemical agents
- Hereditary
- Chromosomal abnormalities
- Deficiency
- Immunologic
- Degenerative
- Organic
- Cancer
- Functional
- Nutritional
- Mental health problems
Infection
Infection is the entry, development, and propagation of a pathogenic agent. There are two types of transmission:
- Direct: Touching any part of the patient.
- Indirect: Through contaminated objects.
Pathogenic Microorganisms
These are microscopic organisms that can cause or spread disease.
Types of Pathogenic Microorganisms
- Bacteria: These are unicellular prokaryotes whose DNA is dispersed throughout the cytoplasm. Outside the membrane, there is a protective bacterial wall. Many bacteria possess another outer gelatinous capsule. Some bacteria are photosynthetic. Bacteria are classified into four types: cocci, bacilli, vibrios, and spirilla.
- Viruses: These are tiny organisms that constitute a sort of bridge between living and inert matter. They are obligate parasites, as they only have the ability to reproduce inside another cell, which they feed on.
- Protozoa: These are unicellular microorganisms that cause diseases, such as malaria, where the vector is a mosquito.
- Fungi: These are very simple organisms that often live in decaying organic matter in the soil. Occasionally, they can parasitize the skin, causing mycosis.
Most Relevant Infectious Diseases
Brucellosis, infectious bacterial conjunctivitis, infectious bacterial or viral diarrhea, diphtheria (bacteria or viruses), bacterial meningitis, bacterial or viral pneumonia, tetanus (bacterium), pertussis (bacterium), tuberculosis (bacterium), bacterial fever, influenza (virus), viral hepatitis, mumps (virus), rabies (virus), rubella (virus), measles (virus), AIDS (virus), varicella (virus), wart (virus), smallpox (virus).
Defense Mechanisms Against Infections
These serve to cope with aggression caused by microorganisms, parasites, and other pathogens from the external environment that can endanger our health or survival.
- External Barriers: Skin, mucous membranes, and hydrochloric acid.
- Internal Defenses: Formed by white blood cells that perform two types of attack:
- Direct: Carried out by some white blood cells called phagocytes. Phagocytosis is the emission of pseudopods to engulf the invader and its subsequent digestion. The set of dead white blood cells is pus.
- Indirect: Performed by two types of white blood cells:
- Lymphocytes: Molecular factories of special proteins called antibodies, whose purpose is to immobilize the invading bacteria or virus.
- Macrophages: Act by engulfing the invader after it has been neutralized by antibodies, thus causing the disappearance of its remains.