Human nutrition 1. Food contains six nutrients, such as sugar, fat, protein, water, inorganic salts and vitamins.
2. Sugar, fat and protein are the main organic substances that make up cells. And can provide energy for life activities.
3. The human body needs inorganic salts containing calcium, phosphorus, iron, iodine and zinc.
4. The main diseases caused by human vitamin deficiency:
Lack of vitamin A: dry skin, night blindness (unclear at night), dry eye, etc.
Vitamin B 1 deficiency: neuritis, beriberi (vitamin B 1 deficiency), indigestion, loss of appetite, etc.
Lack of vitamin C: scurvy, decreased resistance, etc.
Lack of vitamin D: rickets, osteoporosis, etc. Vitamin D can promote the absorption of phosphorus and calcium and bone development.
The process of human digestion and absorption of food is called digestion.
1. The digestive system consists of digestive tract and digestive glands.
2. Digestive tract
(1) Oral cavity, the initial part of digestive tract, including teeth, tongue and salivary glands.
(2) The pharynx and esophagus, the passage of food, are neither digested nor absorbed.
(3) The stomach, the most swollen part of the digestive tract, has the function of temporarily storing food and preliminarily digesting protein.
(4) Small intestine-the main place for digestion and absorption (the duodenum is the initial part of the small intestine)
(5) large intestine-temporary feces, neither digested nor absorbed.
(6) anus
3. Digestive gland
(1) Salivary gland-secretes saliva, and salivary amylase can preliminarily digest starch (
(2) Stomach gland-secretes gastric juice, and pepsin can preliminarily digest protein.
(3) Intestinal gland-secretes intestinal juice, which contains various enzymes and can digest sugar, protein and fat.
(4) Pancreas secretes pancreatic juice, which contains many enzymes and can digest sugar, protein and fat.
(5) liver-secretes bile, does not contain digestive enzymes, and can emulsify fat.
The excretion of wastes in human body 1. Excretion: Excretion refers to the process that animals excrete various foreign substances (drugs, etc.). (urea, uric acid, carbon dioxide, ammonia, etc.) that cannot be reused. ), excessive (water and inorganic salts) and enter the human body during metabolism.
2. Excretion mode
(1) Skin: Water, inorganic salts and urea are excreted in the form of sweat.
(2) Respiratory system: discharging carbon dioxide and water in the form of gas.
(3) Urinary system: Water is discharged in the form of urine. Inorganic salt, urea
Human influence on the biosphere. Human actions to destroy the environment:
Deforestation, environmental pollution, biological invasion, etc
2. Human behavior to protect the environment
Afforestation and establishment of nature reserves
3. The harm of acid rain to the environment
(1) Acid rain will lead to soil acidification.
(2) Acid rain can also induce plant diseases and insect pests, which will greatly reduce crop production.
(3) Acid rain can reduce children's immune function and increase the incidence of chronic pharyngitis and bronchial asthma.
(4) Acid rain can inhibit the reproduction of some soil microorganisms and reduce enzyme activity, and nitrogen-fixing bacteria, bacteria and actinomycetes in the soil will be obviously inhibited by acid rain.
4. The greenhouse effect and the cause of global warming: carbon dioxide emissions.
Structure and function of eyeball 1. Cornea: colorless and transparent, transparent.
2. Sclera: white and tough, protecting the inside of the eyeball (the white part of the eyeball).
3. Iris: pigment (determines the color of the human eye, black, brown, blue, etc. ), and the small hole in the middle is the pupil.
4. Choroid: There are blood vessels (providing nutrition for the eyeball) and pigment cells (shading, forming a "dark room" inside the eyeball).
5. Pupil: the passage through which light enters, the size of which can be adjusted. Pupils shrink in strong light and expand in dark light.
6. Retina: There are a large number of photosensitive cells on the surface, which can feel the stimulation of light and form an object image.
7. Lens: biconvex lens with adjustable curvature, which refracts light and enables eyes to see objects at different distances.
8. Ciliary body: adjust the curvature of the lens.
9. Vitreous body: transparent colloidal substance, which supports the eye ball wall and refracts light.