Ross and Wilson Anatomy and Physiology in Health and Illness

1. The Body's Organization: From Cells to Systems

The cells, tissues and organisation of the body.

Hierarchical Structure. The human body is organized in a hierarchical manner, starting with cells, the basic units of life. Similar cells group together to form tissues, such as epithelial, connective, muscle, and nervous tissue. Different tissues combine to form organs, like the heart or brain, each with specific functions. Finally, organs work together in organ systems, such as the digestive or respiratory system, to perform complex bodily functions.

Maintaining Homeostasis. The body strives to maintain a stable internal environment, a state called homeostasis. This involves regulating factors like temperature, pH, and fluid balance. Various control mechanisms, including feedback loops, work to counteract changes and keep these factors within a narrow range. Disruptions to homeostasis can lead to illness or disease.

Anatomical Terminology. Understanding anatomical terminology is crucial for describing the body's structure and location of its parts. Terms like anterior (front), posterior (back), superior (above), and inferior (below) are used to provide precise directions. Anatomical planes, such as sagittal, frontal, and transverse, divide the body into sections for study and reference.

2. Chemical Foundations: Life's Building Blocks

Introduction to the chemistry of life.

Essential Elements. Life depends on key chemical elements, primarily carbon, hydrogen, oxygen, and nitrogen. These elements combine to form organic molecules, which are the building blocks of living organisms. Water is also crucial, making up a large percentage of the body's mass and serving as a solvent for many chemical reactions.

Macromolecules of Life. The four major classes of organic macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates provide energy, lipids store energy and form cell membranes, proteins perform a wide range of functions including enzymes and structural support, and nucleic acids (DNA and RNA) carry genetic information.

Chemical Reactions. Chemical reactions are essential for life processes, including metabolism, growth, and reproduction. Enzymes are biological catalysts that speed up these reactions. pH, a measure of acidity or alkalinity, is also critical, as enzymes function optimally within a specific pH range.

3. Blood: The River of Life

The blood.

Components of Blood. Blood is a specialized connective tissue composed of plasma, red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Plasma is the liquid matrix, carrying nutrients, hormones, and waste products. Red blood cells transport oxygen, white blood cells fight infection, and platelets are involved in blood clotting.

Functions of Blood. Blood performs several vital functions, including transporting oxygen and nutrients to cells, removing carbon dioxide and waste products, fighting infection, and regulating body temperature. It also plays a role in maintaining fluid balance and pH.

Blood Groups. Blood is classified into different groups based on the presence or absence of specific antigens on the surface of red blood cells. The ABO blood group system and the Rh factor are the most important. Blood transfusions must be compatible to avoid adverse reactions.

4. Cardiovascular System: The Pumping Heart

The cardiovascular system.

Heart Structure. The heart is a muscular organ that pumps blood throughout the body. It consists of four chambers: two atria and two ventricles. Valves ensure that blood flows in one direction. The heart's walls are composed of three layers: the epicardium, myocardium, and endocardium.

Blood Circulation. Blood circulates through two main pathways: pulmonary circulation and systemic circulation. Pulmonary circulation carries blood from the heart to the lungs and back, where it picks up oxygen and releases carbon dioxide. Systemic circulation carries oxygenated blood from the heart to the rest of the body and returns deoxygenated blood to the heart.

Blood Vessels. Blood vessels form a network of tubes that carry blood throughout the body. Arteries carry blood away from the heart, veins carry blood back to the heart, and capillaries are tiny vessels where exchange of nutrients and waste products occurs between blood and tissues. Blood pressure is the force exerted by blood against the walls of blood vessels.

5. Nervous System: The Body's Control Center

The nervous system.

Neurons and Neuroglia. The nervous system is composed of neurons and neuroglia. Neurons are specialized cells that transmit electrical signals called nerve impulses. Neuroglia (glial cells) support, protect, and nourish neurons.

Central and Peripheral Nervous Systems. The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, while the PNS consists of nerves that connect the CNS to the rest of the body.

Brain Regions and Functions. The brain is the control center of the nervous system. Different regions of the brain are responsible for different functions. The cerebrum is involved in higher-level thinking, the cerebellum coordinates movement, and the brainstem controls basic life functions like breathing and heart rate.

6. Endocrine System: Hormonal Harmony

The endocrine system.

Hormones and Glands. The endocrine system consists of glands that secrete hormones into the bloodstream. Hormones are chemical messengers that regulate various bodily functions, including growth, metabolism, and reproduction.

Major Endocrine Glands. Key endocrine glands include the pituitary gland, thyroid gland, adrenal glands, pancreas, and gonads (ovaries and testes). Each gland secretes specific hormones that target particular cells or tissues.

Hormonal Regulation. Hormone secretion is often regulated by feedback loops. Negative feedback loops maintain hormone levels within a narrow range, while positive feedback loops amplify hormone secretion. Disruptions to hormonal balance can lead to various disorders.

7. Respiratory System: The Breath of Life

The respiratory system.

Respiratory Organs. The respiratory system consists of the lungs and the airways that connect them to the outside environment. The airways include the nose, pharynx, larynx, trachea, bronchi, and bronchioles.

Gas Exchange. The primary function of the respiratory system is gas exchange: taking in oxygen and eliminating carbon dioxide. This occurs in the alveoli, tiny air sacs in the lungs, where oxygen diffuses into the blood and carbon dioxide diffuses out.

Breathing Mechanics. Breathing involves the movement of air into and out of the lungs. Inhalation is an active process that requires muscle contraction, while exhalation is usually passive. The rate and depth of breathing are regulated by the brainstem.

8. Digestive System: Fueling the Body

The digestive system.

Digestive Organs. The digestive system consists of the organs that break down food and absorb nutrients. These organs include the mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas, and gallbladder.

Digestive Processes. Digestion involves both mechanical and chemical processes. Mechanical digestion includes chewing and churning, while chemical digestion involves enzymes that break down food molecules.

Nutrient Absorption. Nutrients are absorbed primarily in the small intestine. The small intestine has a large surface area due to the presence of villi and microvilli, which increase the efficiency of absorption. Undigested material passes into the large intestine, where water is absorbed.

9. Urinary System: Waste Management

The urinary system.

Urinary Organs. The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter blood and produce urine, which is then transported to the bladder for storage and eliminated through the urethra.

Kidney Function. The kidneys perform several vital functions, including filtering waste products from the blood, regulating fluid and electrolyte balance, and maintaining blood pressure.

Urine Formation. Urine formation involves three main processes: filtration, reabsorption, and secretion. Filtration occurs in the glomerulus, reabsorption occurs in the tubules, and secretion involves the movement of substances from the blood into the tubules.

10. Skin: The Protective Barrier

The skin.

Skin Layers. The skin is the body's largest organ and serves as a protective barrier. It consists of three layers: the epidermis, dermis, and hypodermis. The epidermis is the outermost layer, the dermis contains blood vessels, nerves, and hair follicles, and the hypodermis is a layer of fat that insulates the body.

Skin Functions. The skin performs several important functions, including protecting the body from injury and infection, regulating body temperature, and sensing touch, pressure, pain, and temperature.

Sensory Receptors. The skin contains various sensory receptors that detect different stimuli. Meissner's corpuscles detect light pressure, Pacinian corpuscles detect deep pressure, and free nerve endings detect pain.

11. Skeleton: The Body's Framework

The skeleton.

Bone Structure. The skeleton provides support and protection for the body. Bones are composed of bone tissue, cartilage, and other connective tissues. Bones are classified by shape, including long bones, short bones, flat bones, and irregular bones.

Bone Functions. Bones perform several important functions, including providing support and shape, protecting internal organs, storing minerals, and producing blood cells.

Joints. Joints are the points where bones meet. They allow for movement and flexibility. Joints are classified by structure and function, including fibrous joints, cartilaginous joints, and synovial joints.

12. Muscles: Movement and More

The muscular system.

Muscle Types. There are three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is responsible for voluntary movement, smooth muscle is found in the walls of internal organs, and cardiac muscle is found in the heart.

Muscle Contraction. Muscle contraction involves the interaction of actin and myosin filaments. Skeletal muscle contraction is initiated by nerve impulses.

Muscle Functions. Muscles perform several important functions, including producing movement, maintaining posture, and generating heat.

Last updated: April 13, 2025