Human Biology PDF

All matter in the universe is composed of one or more unique pure substances called elements, familiar examples of which are hydrogen, oxygen, carbon, nitrogen, calcium, and iron. The smallest unit of any of these pure substances (elements) is an atom. Atoms are made up of subatomic particles such...

All matter in the universe is composed of one or more unique pure substances called elements, familiar examples of which are hydrogen, oxygen, carbon, nitrogen, calcium, and iron. The smallest unit of any of these pure substances (elements) is an atom. Atoms are made up of subatomic particles such as the proton, electron and neutron. Two or more atoms combine to form a molecule, such as the water molecules, proteins, and sugars found in living things. Molecules are the chemical building blocks of all body structures. A cell is the smallest independently functioning unit of a living organism. A human cell typically consists of flexible membranes that enclose cytoplasm, a water-based cellular fluid together with a variety of tiny functioning units called organelles.A tissue is a group of many similar cells (though sometimes composed of a few related types) that work together to perform a specific function. An organ is an anatomically distinct structure of the body composed of two or more tissue types. Each organ performs one or more specific physiological functions. An organ system is a group of organs that work together to perform major functions or meet physiological needs of the body. An organism is a living being that has a cellular structureThe first law of thermodynamics holds that energy can neither be created nor destroyed—it can only change form. Your basic function as an organism is to consume (ingest) energy and molecules in the foods you eat, convert some of it into fuel for movement, sustain your body functions, and build and maintain your body structures. There are two types of reactions that accomplish this: anabolism and catabolism. Anabolism is the process whereby smaller, simpler molecules are combined into larger, more complex substances. Your body can assemble, by utilizing energy, the complex chemicals it needs by combining small molecules derived from the foods you eat Catabolism is the process by which larger more complex substances are broken down into smaller simpler molecules. Catabolism releases energy. The complex molecules found in foods are broken down so the body can use their parts to assemble the structures and substances needed for life. Taken together, these two processes are called metabolism. Metabolism is the sum of all anabolic and catabolic reactions that take place in the body and that can independently perform all physiologic functions necessary for life. Every cell in your body makes use of a chemical compound, adenosine triphosphate (ATP), to store and release energy. The cell stores energy in the synthesis (anabolism) of ATP, then moves the ATP molecules to the location where energy is needed to fuel cellular activities. Then the ATP is broken down (catabolism) and a controlled amount of energy is released, which is used by the cell to perform a particular job. Responsiveness is the ability of an organism to adjust to changes in its internal and external environments. An example of responsiveness to external stimuli could include moving toward sources of food and water and away from perceived dangers. Development is all of the changes the body goes through in life. Development includes the process of differentiation, in which unspecialized cells become specialized in structure and function to perform certain tasks in the body. Development also includes the processes of growth and repair, both of which involve cell differentiation. Growth is the increase in body size. Humans, like all multicellular organisms, grow by increasing the number of existing cells, increasing the amount of non-cellular material around cells (such as mineral deposits in bone), and, within very narrow limits, increasing the size of existing cells. Reproduction is the formation of a new organism from parent organisms. In humans, reproduction is carried out by the male and female reproductive systems. Because death will come to all complex organisms, without reproduction, the line of organisms would end. Atmospheric air is only about 20 percent oxygen, but that oxygen is a key component of the chemical reactions that keep the body alive, including the reactions that produce ATP. Brain cells are especially sensitive to lack of oxygen because of their requirement for a high-and-steady production of ATP. A nutrient is a substance in foods and beverages that is essential to human survival. The three basic classes of nutrients are water, the energy-yielding and body-building nutrients, and the micronutrients (vitamins and minerals). Pressure is a force exerted by a substance that is in contact with another substance. Atmospheric pressure is pressure exerted by the mixture of gasses (primarily nitrogen and oxygen) in the Earth’s atmosphere. Although you may not perceive it, atmospheric pressure is constantly pressing down on your body. This pressure keeps gasses within your body, such as the gaseous nitrogen in body fluids, dissolved. If you were suddenly ejected from a spaceship above Earth’s atmosphere, you would go from a situation of normal pressure to one of very low pressure. The pressure of the nitrogen gas in your blood would be much higher than the pressure of nitrogen in the space surrounding your body. As a result, the nitrogen gas in your blood would expand, forming bubbles that could block blood vessels and even cause cells to break apart. Atmospheric pressure does more than just keep blood gasses dissolved. Your ability to breathe—that is, to take in oxygen and release carbon dioxide—also depends upon a precise atmospheric pressure. A set point is the physiological value around which the normal range fluctuates. A normal range is the restricted set of values that is optimally healthful and stable. For example, the set point for normal human body temperature is approximately 37°C (98.6°F). A negative feedback system has three basic components. A sensor, also referred to a receptor, is a component of a feedback system that monitors a physiological value. This value is reported to the control center. The control center is the component in a feedback system that compares the value to the normal range. If the value deviates too much from the set point, then the control center activates an effector. An effector is the component in a feedback system that causes a change to reverse the situation and return the value to the normal range. Blood Glucose Regulation: When blood glucose levels rise, pancreatic beta cells release insulin, which helps cells absorb glucose, lowering blood sugar levels. When levels drop, insulin release stops. Temperature Regulation: The brain’s heat-loss center activates mechanisms like dilating blood vessels, increasing sweat production, and deeper respiration to cool the body. Conversely, the heat-gain center reduces blood flow to the skin to conserve heat. The anatomical position is a standardized way of describing the human body to avoid confusion. Directional Terms Anterior (or ventral) Describes the front or direction toward the front of the body. The toes are anterior to the foot. Posterior (or dorsal) Describes the back or direction toward the back of the body. The popliteus is posterior to the patella. Superior (or cranial) describes a position above or higher than another part of the body proper. The orbits are superior to the oris. Inferior (or caudal) describes a position below or lower than another part of the body proper; near or toward the tail (in humans, the coccyx, or lowest part of the spinal column). The pelvis is inferior to the abdomen. Lateral describes the side or direction toward the side of the body. The thumb (pollex) is lateral to the digits. Medial describes the middle or direction toward the middle of the body. The hallux is the medial toe. Proximal describes a position in a limb that is nearer to the point of attachment or the trunk of the body. The brachium is proximal to the antebrachium. Distal describes a position in a limb that is farther from the point of attachment or the trunk of the body. The crus is distal to the femur.  Superficial describes a position closer to the surface of the body. The skin is superficial to the bones. Deep describes a position farther from the surface of the body. The brain is deep to the skull. Body Planes A section is a two-dimensional surface of a three-dimensional structure that has been cut. A plane is an imaginary two-dimensional surface that passes through the body. The sagittal plane is the plane that divides the body or an organ vertically into right and left sides. If this vertical plane runs directly down the middle of the body, it is called the midsagittal or median plane. If it divides the body into unequal right and left sides, it is called a parasagittal plane or less commonly a longitudinal section. The frontal plane is the plane that divides the body or an organ into an anterior (front) portion and a posterior (rear) portion. The frontal plane is often referred to as a coronal plane. (“Corona” is Latin for “crown.”) The transverse plane is the plane that divides the body or organ horizontally into upper and lower portions. Transverse planes produce images referred to as cross sections. The dorsal (posterior) cavity and the ventral (anterior) cavity are the largest body compartments. These cavities contain and protect delicate internal organs, and the ventral cavity allows for significant changes in the size and shape of the organs as they perform their functions. The lungs, heart, stomach, and intestines, for example, can expand and contract without distorting other tissues or disrupting the activity of nearby organs. Summary of Body Cavities Posterior (Dorsal) Cavity: Cranial Cavity: Houses the brain. Spinal (Vertebral) Cavity: Encloses the spinal cord. Protection: Both are protected by the skull, vertebral column, and cerebrospinal fluid. Anterior (Ventral) Cavity: Thoracic Cavity: Enclosed by the rib cage, contains the lungs and heart (in the mediastinum), and is separated from the abdominopelvic cavity by the diaphragm. Abdominopelvic Cavity: The largest body cavity, housing digestive organs (abdominal cavity) and reproductive organs (pelvic cavity) Abdominal Regions and Quadrants To promote clear communication, for instance about the location of a patient’s abdominal pain or a suspicious mass, health care providers typically divide up the cavity into either nine regions or four quadrants. Serous Membranes (Serosa): Definition: Thin membranes covering the walls and organs in the thoracic and abdominopelvic cavities. Layers: ○ Parietal Layer: Lines the walls of the body cavity. ○ Visceral Layer: Covers the organs (viscera). Serous Space: A thin, fluid-filled space between the parietal and visceral layers. Types of Serous Cavities and Membranes: 1. Pleura: ○ Cavity: Pleural cavity. ○ Function: Surrounds the lungs, reducing friction between the lungs and body wall. 2. Pericardium: ○ Cavity: Pericardial cavity. ○ Function: Surrounds the heart, reducing friction between the heart and pericardium wall. 3. Peritoneum: ○ Cavity: Peritoneal cavity. ○ Function: Surrounds several organs in the abdominopelvic cavity, reducing friction between these organs and the body wall. Function of Serous Membranes: Cushioning and Reducing Friction: The fluid-filled sacs formed by serous membranes cushion internal organs and reduce friction during movements like lung inflation and heartbeats. Protection: By reducing friction, serous membranes help prevent inflammation of the organs. These membranes play a crucial role in protecting and ensuring the smooth functioning of internal organs. KEY TERMS Abdominopelvic Cavity: A division of the anterior (ventral) cavity that houses the abdominal and pelvic organs. Anabolism: The process of assembling more complex molecules from simpler ones. Anatomical Position: The standard reference position used for describing locations and directions on the human body. Anatomy: The science that studies the form and composition of the body’s structures. Anterior (Ventral): Describes the front or direction toward the front of the body. Anterior Cavity (Ventral Cavity): The larger body cavity located anterior to the posterior (dorsal) body cavity, including the pleural cavities for the lungs, pericardial cavity for the heart, and peritoneal cavity for the abdominal and pelvic organs. Catabolism: The process of breaking down more complex molecules into simpler ones. Caudal (Inferior): Describes a position below or lower than another part of the body, near or toward the tail (coccyx in humans). Cell: The smallest independently functioning unit of all organisms, containing cytoplasm and organelles. Computed Tomography (CT): A medical imaging technique that produces computer-enhanced cross-sectional X-ray images.  Control Center: Compares values to their normal range and activates an effector if deviations occur. Cranial (Superior): Describes a position above or higher than another part of the body. Cranial Cavity: A division of the posterior (dorsal) cavity that houses the brain. Deep: Describes a position farther from the surface of the body. Development: The changes an organism goes through during its life. Differentiation: The process by which unspecialized cells become specialized in structure and function. Distal: Describes a position farther from the point of attachment or the trunk of the body. Dorsal (Posterior): Describes the back or direction toward the back of the body. Dorsal Cavity: The posterior body cavity that houses the brain and spinal cord; also referred to as the posterior body cavity. Effector: An organ that can cause a change in a value. Frontal Plane: A two-dimensional, vertical plane that divides the body or organ into anterior and posterior portions. Gross Anatomy: The study of the larger structures of the body, typically visible to the unaided eye; also referred to as macroscopic anatomy. Growth: The process of increasing in size. Homeostasis: The steady state of body systems that living organisms maintain. Inferior (Caudal): Describes a position below or lower than another part of the body, near or toward the tail (coccyx in humans). Lateral: Describes the side or direction toward the side of the body. Magnetic Resonance Imaging (MRI): A medical imaging technique that uses a magnetic field to obtain detailed sectional images of the internal structures of the body. Medial: Describes the middle or direction toward the middle of the body. Metabolism: The sum of all of the body’s chemical reactions. Microscopic Anatomy: The study of very small structures of the body using magnification. Negative Feedback: A homeostatic mechanism that stabilizes an upset in the body’s physiological condition by preventing an excessive response to a stimulus, typically as the stimulus is removed. Normal Range: The range of values around the set point that do not cause a reaction by the control center. Nutrient: A chemical obtained from foods and beverages that is critical to human survival. Organ: A functionally distinct structure composed of two or more types of tissues. Organ System: A group of organs that work together to carry out a particular function. Organism: A living being that has a cellular structure and can independently perform all physiological functions necessary for life. Pericardium: The sac that encloses the heart. Peritoneum: The serous membrane that lines the abdominopelvic cavity and covers the organs found there. Physiology: The science that studies the chemistry, biochemistry, and physics of the body’s functions1. Plane: An imaginary two-dimensional surface that passes through the body. Pleura: The serous membrane that lines the pleural cavity and covers the lungs. Positive Feedback: A mechanism that intensifies a change in the body’s physiological condition in response to a stimulus. Positron Emission Tomography (PET): A medical imaging technique in which radiopharmaceuticals are traced to reveal metabolic and physiological functions in tissues. Posterior (Dorsal): Describes the back or direction toward the back of the body.  Posterior Cavity (Dorsal Cavity): The posterior body cavity that houses the brain and spinal cord. Pressure: The force exerted by a substance in contact with another substance. Prone: Lying face down. Proximal: Describes a position nearer to the point of attachment or the trunk of the body. Regional Anatomy: The study of the structures that contribute to specific body regions. Renewal: The process by which worn-out cells are replaced. Reproduction: The process by which new organisms are generated. Responsiveness: The ability of an organism or a system to adjust to changes in conditions. Sagittal Plane: A two-dimensional, vertical plane that divides the body or organ into right and left sides. Section: In anatomy, a single flat surface of a three-dimensional structure that has been cut through. Sensor (Receptor): Reports a monitored physiological value to the control center. Serosa (Serous Membrane): A membrane that covers organs and reduces friction. Set Point: The ideal value for a physiological parameter, within which it is stable and optimally healthful. Spinal Cavity (Vertebral Cavity): A division of the dorsal cavity that houses the spinal cord. Superficial: Describes a position nearer to the surface of the body. Superior (Cranial): Describes a position above or higher than another part of the body. Supine: Lying face up. Systemic Anatomy: The study of the structures that contribute to specific body systems. Thoracic Cavity: A division of the anterior (ventral) cavity that houses the heart, lungs, esophagus, and trachea. Tissue: A group of similar or closely related cells that act together to perform a specific function. Transverse Plane: A two-dimensional, horizontal plane that divides the body or organ into superior and inferior portions. Ultrasonography: The application of ultrasonic waves to visualize subcutaneous body structures such as tendons and organs. Ventral (Anterior): Describes the front or direction toward the front of the body. Ventral Cavity (Anterior Body Cavity): The larger body cavity located anterior to the posterior (dorsal) body cavity, including the pleural cavities for the lungs, pericardial cavity for the heart, and peritoneal cavity for the abdominal and pelvic organs. X-ray: A form of high-energy electromagnetic radiation with a short wavelength capable of penetrating solids and ionizing gasses, used in medicine as a diagnostic aid to visualize body structures such as bones.