The Human Body: An Orientation PDF

# The Human Body: An Orientation ## Anatomy - the study of the structure and shape of the body and body parts & their relationships to one another - the term anatomy comes from the Greek words meaning to cut (tomy), apart (ana) ### Gross Anatomy (Macroscopic Anatomy) - the study of large, easily o...

# The Human Body: An Orientation ## Anatomy - the study of the structure and shape of the body and body parts & their relationships to one another - the term anatomy comes from the Greek words meaning to cut (tomy), apart (ana) ### Gross Anatomy (Macroscopic Anatomy) - the study of large, easily observable structures by the naked eye, such as the heart or bone ### Microscopic Anatomy (Cytology, Histology) - the study of very small structures, where a magnifying lens or microscope is needed. ## Relationship Between Anatomy and Physiology - Structure determines what functions can take place. - For example, the lungs are not muscular chambers like the heart and cannot pump blood, but because the walls of lungs are very thin, they can exchange gases and provide oxygen to the body. ## Levels of Structural Organization - The human body exhibits 6 levels of structural complexity. ### 1. Chemical Level - The simplest level of structural ladder. - At this level, atoms combine to form molecules, such as water, sugar, and proteins. ### 2. Cellular Level - The smallest units of living things. ### 3. Tissue Level - Groups of similar cells that have a common function. - There are four basic types of tissues. ### 4. Organ Level - A structure composed of 2 or more tissue types that performs a specific function. ### 5. Organ System - A groups of organs that work together to accomplish a common purpose. - Each organ has its own job to do. ### 6. Organismal Level - The highest level of structural organization - The human body consists of 11 organ systems. A diagram of a woman running shows six levels of organization from atoms and molecules to the organismal level. ## Body Systems - The human body has 11 systems. ### 1. Integumentary System - **Organs:** Skin - **Functions:** - Water proofs, cushions, protects deeper tissue - Excretes salts & urea; pain, pressure ### 2. Skeletal System - **Organs:** Bones, cartilages, ligaments, joints - **Functions:** - Protects & supports body organs - Framework for muscles & movement ### 3. Muscular System - **Organs:** Skeletal muscle - **Functions:** - Contraction & mobility ### 4. Nervous System - **Organs:** Brain, spinal cord, nerves, & sensory receptors - **Functions:** - Fast-acting central control system ### 5. Endocrine System - **Organs:** Pituitary, thyroid, parathyroids, adrenals, thymus, pancreas, pineal, ovaries, testes - **Functions:** - Slow-acting control system ### 6. Circulatory System - **Organs:** Heart, blood vessels, capillaries & blood - **Functions:** - Carries O2, nutrients, hormones, & other substances to and from tissue cells - White blood cells protect against bacteria, toxins, tumors ### 7. Lymphatic System - **Organs:** Lymphatic vessels, lymph nodes, spleen, tonsils - **Functions:** - Complements circulatory system by returning leaked fluid back to blood vessels - Cleanses the blood; involved in immunity ### 8. Respiratory System - **Organs:** Nasal cavity, pharynx, larynx, trachea, bronchi, & lungs - **Functions:** - Keeps blood supplied with O2 & removes CO2 - Carries out gas exchanges through air sacs in lungs ### 9. Digestive System - **Organs:** Oral cavity, esophagus, stomach, small intestine, large intestine, rectum, anus (liver & pancreas) - **Functions:** - Breaks food down into absorbable units that enter the blood - Indigestible food eliminated as feces ### 10. Urinary (Excretory) System - **Organs:** Kidney, ureter, urinary bladder, urethra - **Functions:** - Eliminates nitrogenous waste from the body (urea & uric acid) - Regulates water, electrolytes, & acid-base balance of the blood ### 11. Reproductive System - **Organs:** - **Male:** Seminal vesicles, prostate, penis, vas deferens, testis, scrotum - **Female:** Ovaries, mammary glands, uterus, vagina, uterine tube - **Functions:** - Primary function for both sexes is to produce offspring - **Male:** Testes produce sperm & male sex hormones - **Female:** Ovaries produce eggs & female sex hormones; mammary glands for nourishment A diagram shows systems working together to maintain life in the human body. The digestive system breaks down food. The circulatory system carries nutrients and oxygen to cells. The respiratory system provides oxygen. The urinary and respiratory systems expel waste. ## Maintaining Life - To maintain life, the body must have necessary life functions and survival needs. ### I. Necessary Life Functions - All living organisms carry out certain vital functional activities necessary for life. - All of the below are necessary life functions: #### 1. Maintenance of Boundaries: - Every living organism maintains its inside distinct from outside. - All cells are surrounded by a selectively permeable membrane. - The body as a whole is enclosed and protected by the integumentary system or skin, which protects our internal organs from drying out, bacteria, heat, sunlight, and chemicals. #### 2. Movement: - Includes activities promoted by the muscular system. - The skeletal system provides a bony framework that muscles pull on. - Movement also occurs when substances such as blood, foodstuffs, and urine are propelled through internal organs. - On the cellular level, the muscle cell's ability to move by shortening is more precisely called contractility. #### 3. Responsiveness or Irritability: - The ability to sense changes (stimuli) in the environment and then respond to them. - For example, you involuntarily pull your hand away from the painful stimulus. - When carbon dioxide in your blood rises to dangerously high levels, your breathing rate speeds up. - Nerve cells are highly irritable and communicate rapidly with each other via electrical impulses. The nervous system is most involved with responsiveness but all body cells are irritable to some extent. #### 4. Digestion: - The breaking down of ingested foodstuffs to simple molecules that can be absorbed into the blood. - The nutrient-rich blood is then distributed to all body cells by the cardiovascular system. - In a simple, one-celled organism such as an amoeba, the cell itself is the "digestion factory," but in the multicellular human body, the digestive system performs this function for the entire body. #### 5. Metabolism: - A broad term that includes all chemical reactions that occur within body cells. - Includes breaking down substances into their simpler building blocks (catabolism), synthesizing more complex cellular structures from simpler substances (anabolism), and using nutrients and oxygen to produce (via cellular respiration), ATP, that power cellular activities. - Metabolism depends on the digestive and respiratory systems to make nutrients and oxygen available to be distributed throughout the body. - Metabolism is regulated largely by hormones secreted by endocrine system glands. #### 6. Excretion: - The process of removing excreta or wastes, from the body. - The digestive system rids the body of indigestible food residues in feces - The urinary system disposes of nitrogen-containing metabolic wastes, such as urea, in urine. - Carbon dioxide, a by-product of cellular respiration, is carried in the blood to the lungs, where it leaves the body in exhaled air. #### 7. Reproduction: - Making a whole new person which is the major task of the reproductive system. - When a sperm unites with an egg, a fertilized egg forms, which then develops into a baby within the mother's body. - The reproductive system is regulated by hormones of the endocrine system. - Because males produce sperm and females produce eggs (ova), there is a division of labor in the reproductive process, and the reproductive organs of males and females are different. - The female's reproductive structures provide the site for fertilization of eggs by sperm, then protect and nurture the developing fetus until birth. #### 8. Growth - An increase in size of a body part or the organism. - Usually accomplished by increasing the number of cells. - Individual cells also increase in size when not dividing. - For true growth to occur, constructive activities must occur at a faster rate than destructive ones. ### II. Survival Needs: - These needs include: #### 1. Nutrients: - Taken in via the diet. - Contain the chemical substances used for energy and cell building. - Carbohydrates are the major energy fuel for body cells. - Proteins, and to a lesser extent fats, are essential for building cell structures. - Fats also provide a reserve of energy-rich fuel. - Selected minerals and vitamins are required for the chemical reactions that go on in cells and for oxygen transport in the blood. - The mineral calcium helps to make bones hard and is required for blood clotting. #### 2. Oxygen: - All the nutrients in the world are useless unless oxygen is also available. - Chemical reactions that release energy from foods are oxidative reactions that require oxygen. - Human cells can survive for only a few minutes without oxygen. - Approximately 20% of the air we breathe is oxygen. - It is made available to the blood and body cells by the cooperative efforts of the respiratory and cardiovascular systems. #### 3. Water: - Accounts for 60-80% of body weight and is the single most abundant chemical substance in the body. - Provides the watery environment necessary for chemical reactions and the fluid base for body secretions and excretions. - Obtained chiefly from ingested foods or liquids and is lost from the body by evaporation from the lungs and skin and in body excretions. #### 4. Normal Body Temperature: - If chemical reactions are to continue at life-sustaining rates, normal body temperature must be maintained. - As body temperature drops below 37°C (98.6°F), metabolic reactions become slower and slower, and finally stop. - When body temperature is too high, body proteins lose their characteristic shape and stop functioning. - At either extreme, death occurs. - Most body heat is generated by the activity of the muscular system. #### 5. Atmospheric Pressure: - The force that air exerts on the surface of the body. - Breathing and gas exchange in the lungs depend on appropriate atmospheric pressure. - At high altitudes, where atmospheric pressure is lower and the air is thin, gas exchange may be inadequate to support cellular metabolism. - The mere presence of these survival factors is not sufficient to sustain life. - They must be present in appropriate amounts; excesses and deficits may be equally harmful. - For example, the food we eat must be of high quality and in proper amounts; otherwise, nutritional disease, obesity, or starvation is likely. ## Homeostasis - Describes the body's ability to maintain relatively stable internal conditions even though the outside world is continuously changing. - Literally translates to “unchanging." Homeo= the same, stasis= standing still. This is not actually true. - The term does not really mean a static, or unchanging, state. - It indicates a dynamic state of equilibrium, or a balance, in which internal conditions vary, but always within relatively narrow limits. - The body is in homeostasis when its needs are adequately met and it is functioning smoothly. ### Homeostatic Control Mechanisms - Communication within the body is essential for homeostasis. - Accomplished chiefly by the nervous and endocrine systems. - These systems use neural electrical impulses or blood borne hormones, respectively, as information carriers. - Regardless of the factor being regulated, homeostatic control mechanisms have 3 interdependent components. #### Components of Homeostatic Control Mechanisms: ##### 1. Receptor: - A sensor that monitors the environment - Responds to changes, called stimuli, by sending information (input) to the control center. ##### 2. Control Center: - Analyzes the input it receives and determines the appropriate response or course of action. - Input flows from the receptor to the control center along the afferent pathway. ##### 3. Effector: - Provides the means of response (output) to the stimulus. - Information flows from the control center to the effector along the efferent pathway. - The results of the response then feed back to influence the stimulus. #### Feedback Systems: ##### Negative Feedback: - The net effect of the response to the stimulus is the shut off of the original stimulus or reduce its intensity. - Examples: Body temp, blood chemical levels ##### Positive Feedback: - Tends to increase the original disturbance (stimulus) and push the variable farther from its original value. - Examples: Ovulation, blood clotting and birth A diagram shows how the body maintains a stable internal environment through negative feedback. - **The receptor** senses changes (stimuli). - **The control center** determines the appropriate response. - **The effector** carries out the response. - The response then feeds back to influence the stimulus, returning the variable to homeostasis. ### Homeostatic Imbalance - Homeostasis is so important that most disease can be regarded as a result of its disturbance. - A condition called homeostatic imbalance. - As we age, our body's control systems become less efficient, and our internal environment becomes less and less stable. - These events increase our risk for illness and produce the changes we associate with aging. - Examples of homeostatic imbalance are provided throughout this course to enhance understanding of normal physiological mechanisms. ## The Language of Anatomy ### Anatomical Position - Standing erect - Feet parallel - Arms hanging at the sides - Palms facing forward - A person is said to be in anatomical position if their body is erect with the feet parallel and the arms hang at the sides with palms facing forward. - Most terminology refers to this position, regardless of the position the body happens to be in. ### Directional Terms - **Superior (cranial or cephalad)**: Toward the head end or upper part of a structure of body; above. - **Inferior (caudal)**: away from the head end or toward the lower part of a structure or body; below. - **Anterior (ventral)**: Toward or at the front of the body; in front of. - **Posterior (dorsal)**: Toward or at the backside of the body; behind. - **Medial**: Toward or at the midline of the body; on the inner side of. - **Lateral**: Away from the midline of the body; on the outer side of. - **Proximal**: Close to the origin of the body part or the point of attachment of a limb to the body trunk. - **Distal**: Farther from the origin of a body or the point of attachment of a limb to the body trunk. - **Superficial (external)**: Toward or at the body surface. - **Deep (internal)**: Away from the body surface; more internal. ### Examples: - The navel is inferior to the breastbone. - The heart is posterior to the breastbone. - The arms are lateral to the chest. - The elbow is proximal to the wrist. - The skin is superficial to the skeleton. - The forehead is superior to the nose. - The breastbone is anterior to the spine. - The heart is medial to the arm. - The armpit is intermediate between the breastbone and the shoulder. - The knee is distal to the thigh. - The lungs are deep to the rib cage. ### Body Planes and Sections - **A section** is a cut made along a plane. - **Sagittal**: A cut made along the lengthwise or longitudinal plane of the body dividing it into left and right parts. - **Midsagittal (median) plane**: Right and left parts are of equal size. - **Frontal (coronal) plane**: Cut made along a lengthwise plane that divides the body into anterior and posterior parts. - **Transverse plane (cross section)**: Cut made along a horizontal plane dividing the body or into superior and inferior parts. ### Regional Terms - There are many visible landmarks on the surface of the body. - **Anterior Body Landmarks**: Anterior landmarks include: - Nasal - Oral - Cervical - Acromial - Thoracic - Brachial - Ante cubital - Abdominal - Umbilical - Carpal - Digital - Pubic - Patellar - Crural - Tarsal - **Posterior Body Landmarks**: Posterior landmarks include: - Occipital - Deltoid - Scapular - Vertebral - Olecranal - Lumbar - Sacral - Gluteal - Popliteal - Sural ### Body Cavities - Two sets of internal body cavities: - **Dorsal Body Cavities**: These cavities protect the fragile nervous system organs. - **Cranial Cavity**: Encases the brain, in the skull. - **Vertebral (spinal) Cavity**: Runs within the bony vertebral column, encloses the delicate spinal cord. - The cranial and spinal cavities are continuous. - **Ventral Body Cavities**: The more anterior and larger of the closed body cavities. - The ventral body cavity has two major subdivisions: - **Thoracic Cavity**. - **Abdominopelvic Cavity**: - **Pelvic Cavity**: The inferior part of the abdominopelvic cavity, which lies in the pelvis. - The thoracic and abdominopelvic cavities are separated by the diaphragm. - The abdominopelvic cavity houses internal organs collectively called the viscera. - The abdominopelvic cavity is not physically separated into the abdominal cavity and the pelvic cavity. ### Homeostatic Imbalance - When the body is subjected to physical trauma, abdominopelvic organs are most vulnerable because the walls of the abdominal cavity are formed only by trunk muscles and are not reinforced by bone. - Pelvic organs receive a greater degree of protection from the bony pelvis. #### Abdominopelvic Regions and Quadrants - The abdominopelvic cavity is large and contains several organs. - For study it is helpful to divide into smaller areas. - **Regional Method**: Two transverse and two parasagittal planes, divide the cavity into 9 regions. - **Quadrant Method**: One transverse and one median sagittal plane pass through the umbilicus at right angles. #### Regional Method: - **Umbilical Region**: Deep to and surrounding the umbilicus (navel) - **Epigastric Region**: Superior to the umbilical region (epi= upon, above; gastri= belly) - **Hypogastric (Pubic) Region**: Inferior to the umbilical region (hypo = below) - **Right and Left Iliac or Inguinal Regions**: Lateral to the hypogastric region (iliac= superior part of the hip bone) - **Right and Left Lumbar Regions**: Lateral to the umbilical region (lumbus= loin) - **Right and Left Hypochondriac Regions**: Flank the epigastric region laterally (chondro= cartilage) #### Quadrant Method: - **Right Upper Quadrant**: RUQ - **Left Upper Quadrant**: LUQ - **Right Lower Quadrant**: RLQ - **Left Lower Quadrant**: LLQ