Human Biology Lecture 1 PDF

# Contents 1. Introduction. 2. Digestive system, digestion and nutrition. 3. Circulatory system and circulation. 4. The Lymphatic system. 5. Immune system and immunity. 6. Respiratory system and respiration. 7. Excretory system and excretion. 8. Endocrine system and hormones. 9. The nervous system...

# Contents 1. Introduction. 2. Digestive system, digestion and nutrition. 3. Circulatory system and circulation. 4. The Lymphatic system. 5. Immune system and immunity. 6. Respiratory system and respiration. 7. Excretory system and excretion. 8. Endocrine system and hormones. 9. The nervous system and nerve impulse transmission. 10. Muscles and muscle contraction. 11. Skeletal system and bones. 12. Human reproductive system and reproduction. # 1. Introduction ## 1.1. Levels of organization of human body: ### 1.1.1. Chemical level: * This is the simplest level within the structural hierarchy. * The chemical level includes all of the chemical substances essential (atoms) for maintaining life. * Atoms combine to form molecules, which may be simple or complex. * For example, hydrogen and oxygen atoms combine to form a molecule of water H₂O, which is essential for survival of the body. * Saliva, tears and many other body fluids are made of water. * Different types of molecules combine to form organelles (the internal organs of a cell). * Organelles are specific structures that carry out specific functions. ### 1.1.2. Cellular level: * The cellular level is made up of the smallest unit of living matter, the cell. * Cells are the basic structural and functional units of all living things. * The human body is composed of trillions of cells. * Cells have many parts, called organelles, each with a different function. * When a human life begins, it starts as a single cell and grows as those cells multiply through mitosis, which makes sure the cellular structure established by the single cell is replicated over and over again and that the body gets a full set of 46 chromosomes. * The other major function on the cellular level is cellular differentiation, which facilitates the specific functions of cells and genes in the human body. ### 1.1.3. Tissue level: * Tissues are groups of similar cells that have a common function. * The four basic tissue types in humans include epithelium, connective, muscle, and nervous tissue. ### 1.1.4. Organ level: * An organ is a structure composed of at least two different tissue types that perform a specific function within the body. * Examples include the brain, heart, lungs, stomach, liver, skin, and kidneys. ### 1.1.5. Organ system level: #### 1.1.5.1. Definition of organ system: * One or more organs work in unison to accomplish a common purpose. * For instance, the heart and blood vessels work together and circulate blood throughout the body to provide oxygen and nutrients to cells. * Besides the cardiovascular system, the other organ systems of the body are the integumentary, skeletal, nervous, muscular, endocrine, respiratory, lymphatic, digestive, urinary, and reproductive systems. #### 1.1.5.2. Types of human body systems: * **Integumentary system:** Forms the external body covering and protects deeper tissues from injury. Houses coetaneous receptors, sweat glands, oil glands, and synthesizes vitamin D. * **Skeletal system:** Supports and protects the body's organs. Provides a framework muscles use (movement). Bones also store minerals and create blood cells. * **Muscular system:** Maintains posture and produces movement (locomotion). Produces heat. * **Lymphatic system:** Houses white blood cells (lymphocytes) involved in immunity. Returns leaked fluid from blood vessels to the blood and disposes debris within the lymphatic stream. * **Respiratory system:** Removes carbon dioxide and continually supplies blood with oxygen. Gaseous exchanges occur in the respiratory system (lungs). * **Digestive system:** Breaks down food to be absorbed and eliminates indigestible waste. * **Nervous system:** Control system of the body, responds to internal and external changes, activates muscles and glands. * **Endocrine system:** Glands from the endocrine system secrete hormones that regulate many processes like growth, metabolism, and reproduction. * **Cardiovascular system:** The heart pumps blood and blood vessels transport it. Blood carries oxygen, carbon dioxide, nutrients, waste and more throughout the body. * **Urinary system:** Eliminates nitrogenous wastes from the body. Regulates acid-base, electrolyte and water balance of blood. * **Reproductive systems:** The main function of the reproductive system is to produce offspring. Sex hormone and sperm are produced by the male testes. Male ducts and glands help deliver the sperm. Ovaries produce female sex hormones and eggs. Other female reproductive structures serve as sites of fertilization and development. For instance, the mammary glands produce milk for the newborn. ### 1.1.6. Organism level: * The organism level is the highest level of organization. * It is the sum total of all structural levels working together. * In short, it is the human being (or organism ) as a whole. A diagram of all the organ systems of the human body was included in this document.