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CHAPTER I: AN INTRODUCTION TO HUMAN BODY
Human Body and Homeostasis 1.1 ANATOMY AND PHYSIOLOGY Anatomy and Physiology The structure of a part of the body often reflects its functions. For example, the bones of the skull join tightly to form a rigid case that protects the brain. The bones of the fingers are more loosely joined to allow a variety of movements. The walls of the air sacs in the lungs are very thin, permitting rapid movement of inhaled oxygen into the blood. Anatomy - the science of body structures and the relationships among them. ● “ana” – up; “tomy” – process of cutting Dissection ( dis = apart; section = act of cutting) - careful cutting apart of body structures to study their relationships. deals with structures of the body. Physiology - the science of body functions—how the body parts work. “physio” = nature; “logy” = study of BRANCHES OF ANATOMY AND PHYSIOLOGY Embryology (embry- = embryo; -logy = study of) – study of the first eight weeks of development after fertilization of a human egg. Developmental biology – study of the complete development of an individual from fertilization to death. Cell biology – study of cellular structure and functions. Histology (hist- = tissue) – study of microscopic structure of tissues. Gross anatomy – study of structures that can be examined without a microscope. Systemic anatomy – study of structure of specific systems of the body such as the nervous or respiratory systems. Regional anatomy – study of specific regions of the body such as the head or chest. Surface anatomy – study of surface markings of the body to understand internal anatomy through visualization and palpation (gentle touch). Imaging anatomy – study of internal body structures that can be visualized with techniques such as x-rays, MRI, CT scans, and other technologies for clinical analysis and medical intervention.
Pathological anatomy (path- = disease) – study of structural changes (gross to microscopic) associated with disease. Molecular Physiology – study of the functions of individual molecules such as proteins and DNA. Neurophysiology (neuro- = nerve) – study of the functional properties of nerve cells. Endocrinology (endo- = within; -crin = secretion) – study of the hormones (chemical regulators in the blood) and how they control body functions. Cardiovascular Physiology (cardi- = heart; vascular = blood vessels) – study of the functions of the heart and blood vessels. Immunology (immun- = not susceptible) – study of the body’s defenses against disease-causing agents. Respiratory Physiology (respira- = to breathe) – study of the functions of the air passageways and lungs. Renal Physiology (ren- = kidney) – study of the functions of the kidneys. Exercise Physiology – study of the changes in cell and organ functions due to muscular activity. Pathophysiology – study of the functional changes associated with disease and aging. 1.2 LEVELS OF STRUCTURAL ORGANIZATION AND BODY SYSTEM
1. Chemical Level – very basic level Atoms – smallest unit of matter that participates in chemical reactions. - carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), calcium (Ca), and sulfur (S), are essential for maintaining life. Molecules – two or more atoms joined together. - deoxyribonucleic acid (DNA), the genetic material passed from one generation to the next, and glucose, commonly known as blood sugar. 2. Cellular Level – molecules combine to form cells. Cells – the basic structural and functional units of an organism that are composed of chemicals. - smallest living units in the human body. - muscle cells, nerve cells, and epithelial cells. 3. Tissue Level – tissue Tissues – are groups of cells and the materials surrounding them that work together to perform a particular function.
Noninvasive Diagnostic Techniques
- to assess certain aspects of body structure and function. Noninvasive diagnostic technique – one that does not involve insertion of an instrument or device through the skin or a body opening. Inspection – the examiner observes the body for any changes that deviate from normal. For example, a physician may examine the mouth cavity for evidence of disease. Palpation – (palp- = gently touching) the examiner feels body surfaces with the hands. An example is palpating the abdomen to detect enlarged or tender internal organs or abnormal masses. Auscultation – (auscult- = listening) the examiner listens to body sounds to evaluate the functioning of certain organs, often using a stethoscope to amplify the sounds. An example is auscultation of the lungs during breathing to check for crackling sounds associated with abnormal fluid accumulation. Percussion – (percus- = beat through) the examiner taps on the body surface with the fingertips and listens to the resulting sound. Hollow cavities or spaces produce a diff erent sound than solid organs. For example, percussion may reveal the abnormal presence of fluid in the lungs or air in the intestines. It may also provide information about the size, consistency, and position of an underlying structure.
1.3 CHARACTERISTICS OF THE LIVING HUMAN ORGANISMS
BASIC LIFE PROCESSES
Metabolism – the sum of all chemical processes that occur in the body. ● Catabolism – (catabol- = throwing down; -ism = a condition) the breakdown of complex chemical substances into simpler components. ● Anabolism – (anabol- = a raising up) the e building up of complex chemical substances from smaller, simpler components. For example, digestive processes catabolize (split) proteins in food into amino acids. These amino acids are then used to anabolize (build) new proteins that make up body structures such as muscles and bones. Responsiveness – the body’s ability to detect and respond to changes.
- For example, an increase in body temperature during a fever represents a change in the internal environment (within the body), and turning your head toward the sound of squealing brakes is a response to a change in the external environment (outside the body) to prepare the body for a potential threat.
- Nerve cells respond by generating electrical signals known as nerve impulses. Movement – includes s motion of the whole body, individual organs, single cells, and even tiny structures inside cells.
- the coordinated action of leg muscles moves your whole body from one place to another when you walk or run. Aft er you eat a meal that contains fats, your gallbladder contracts and releases bile into the gastrointestinal tract to help digest them.
- When a body tissue is damaged, white blood cell move from the bloodstream into the affected tissue to help to help clean up and repair the area. Growth – an increase in body size that results from an increase in the size of existing cells, an increase in the number of cells, or both.
- a tissue sometimes increases in size because the amount of material between cells increases. Differentiation – the development of a cell from an unspecialized to a specialized state.
- precursor cells , which can divide and give rise to cells that undergo differentiation, are known as stem cells.
- red blood cells and several types of white blood cells all arise from the same unspecialized precursor cells in red bone marrow.
- through differentiation, a single fertilized human egg (ovum) develops into an embryo, and then into a fetus, an infant, a child, and finally an adult. Reproduction – the formation of new cells for tissue growth, repair, or replacement; the production of a new individual.
How does a nutrient in the external environment reach a body cell? Sure, let's break it down in a simple way:
1. Integumentary System (Skin) – this is like the body's outer armor. It doesn't directly exchange stuff, but it protects us from harm outside. 2. Respiratory System (Lungs) – it lets oxygen from the air enter our blood.
- Digestive System (Stomach, Intestines) – it allows nutrients from food to enter our blood.
- Cardiovascular System (Heart and Blood Vessels) – it's like our body's internal transportation system. It carries oxygen and nutrients all around. 5. Blood Capillaries – these are tiny blood vessels that act like little bridges between our blood and our cells. They let oxygen and nutrients move from the blood to the cells and take waste products from cells back to the blood.
6. Cells – these are like the body's workers. They use oxygen and nutrients for energy and make waste. 7. Waste Products – when cells work, they make waste. This waste goes into the spaces around cells (interstitial fluid). 8. Cardiovascular System Again – it picks up these wastes and takes them to the organs responsible for getting rid of them. 9. Respiratory System – it gets rid of one type of waste, which is carbon dioxide (CO2), by letting us breathe it out. 10. Urinary System (Kidneys and Bladder) – it gets rid of other waste products like urea and ammonia by making us pee them out. So, all these systems work together to make sure our body stays clean inside, with the right nutrients going in and waste going out. It's like a big team effort to keep us healthy! CONTROL OF HOMEOSTASIS Homeostasis in the human body is the process of maintaining a stable internal environment despite external and internal disruptions. These disruptions can come from things like extreme weather, lack of oxygen during exercise, skipped meals, or psychological stress. In most cases, the body's cells respond quickly to these disruptions and restore balance. However, in more severe situations like poisoning, extreme temperature exposure, serious infections, or major surgery, the disruption can be intense and prolonged. Nervous System – regulates homeostasis by sending electrical signals known as nerve impulses (action potentials) to organs that can counteract changes from the balanced state. Regulating System: Nerve Impulses (Action Potential) – electrical signal; cause rapid changes. Hormones – glands that secrete messenger molecules; usually work more slowly. Feedback System (Feedback loop) – a cycle of events in which the status of a body condition is monitored, evaluated, changed, remonitored, reevaluated, and so on. Controlled Condition – this is what the body is trying to monitor, like body temperature, blood pressure, or blood glucose levels. Stimulus – any disruption that changes the controlled condition. Components of Feedback System:
What is the main difference between negative and positive feedback systems? Negative Feedback System – reverses a change in a controlled condition. ● Reverses changes in the body to maintain stability. ● Example: Blood pressure rises, sensors detect it, brain sends signals to lower heart rate and widen blood vessels to bring pressure back to normal. ● Keeps the body in balance and stops when things are back to normal. Positive Feedback System – tends to strengthen or reinforce a change in one of the body’s controlled conditions. ● Amplifies changes in the body, making them stronger. ● Example 1: During childbirth, contractions get stronger as the cervix stretches, pushing the baby out. ● Example 2: Severe blood loss makes the heart weaker, leading to more blood loss. ● Requires an external event to stop it; can become dangerous if left unchecked. In short, negative feedback maintains stability, while positive feedback amplifies changes and can be risky if not stopped.
Homeostatic Imbalances Homeostasis
- Affected by factors like environment, genetics, what you eat, and how you live.
- Diseases often result from years of bad habits, like smoking.
- It's better to prevent problems by living a healthy lifestyle than to rely on doctors to fix them.
- When everything in the body stays balanced, cells work well, and you stay healthy.
- If something disrupts this balance, it can lead to disorders or even death.
Regional Names ● Head : Includes the skull and face; protects the brain and houses features like eyes, nose, mouth, and chin. ● Neck : Supports and connects the head to the trunk. ● Trunk : Comprises the chest, abdomen, and pelvis. ● Upper Limbs : Attach to the trunk and consist of the shoulder, armpit, arm, forearm, wrist, and hand. ● Lower Limbs : Also attach to the trunk and include the buttock, thigh, leg, ankle, and foot.
● Groin: The area on the front of the body, marked by a crease on each side, where the trunk joins the thighs. Directional Terms Directional Terms – words that describe the position of one body part relative to another. Several directional terms are grouped in pairs that have opposite meanings, such as anterior (front) and posterior (back).
Transverse Plane – divides the body or an organ into superior (upper) and inferior (lower) portions. Other names for a transverse plane are a cross-sectional or horizontal plane. Oblique Plane – passes s through the body or an organ at an oblique angle (any angle other than a 90-degree angle). Section – when you study a body region, you often view it in section. It is a cut of the body or one of its organs made along one of the planes just described. It is important to know the plane of the section so you can understand the anatomical relationship of one part to another.
Body Cavities Body Cavities - spaces that enclose internal organs. Bones, muscles, ligaments, and other structures separate the various body cavities from one another. Cranial Cavity - cranial bones form a hollow space of the head, which contains the brain. Vertebral Column (Backbone) to Vertebral (Spinal) Canal - which contains the spinal cord. Meninges – three layers of protective tissue Major Body Cavities of the Trunk Thoracic Cavity (Chest Cavity) - formed by the ribs, the muscles of the chest, the sternum (breastbone), and the thoracic portion of the vertebral column. Pericardial Cavity – within the thoracic, a fluid-filled space that surrounds the heart, and two fluid-filled spaces called pleural cavities. Mediastinum – between the lungs, extending from the sternum to the vertebral column and from the first rib to the diaphragm. Contains all thoracic organs except the lungs themselves. Diaphragm – a dome-shaped muscle that separates the thoracic cavity from the abdominopelvic cavity. Abdominopelvic Cavity – extends from the diaphragm to the groin and is encircled by the abdominal muscular wall and the bones and muscles of the pelvis. Abdominal Cavity – superior portion contains the stomach, spleen, liver, gallbladder, small intestine, and most of the large intestine. Pelvic Cavity – inferior portion contains the urinary bladder, portions of the large intestine, and internal organs of the reproductive system. Organs inside the thoracic and abdominopelvic cavities are called viscera.
