Week 1 - Human Biology 1 - Body Orientation PDF

Human Biology 1 Learning Outcomes • By the end of this session you will be able to: • Define human anatomy and physiology • Describe the levels of structural organization of the body. • Identify features of living systems • Describe the principles of homeostasis and feedback systems Check your u...

Human Biology 1 Learning Outcomes • By the end of this session you will be able to: • Define human anatomy and physiology • Describe the levels of structural organization of the body. • Identify features of living systems • Describe the principles of homeostasis and feedback systems Check your understanding 1. Can you define…… • Anatomy? • Physiology? • Homeostasis? 2. Can you name 4 systems of the human body? 3. Why is a knowledge of physiology important? (Why are we studying it??!! Anatomy: • The branch of science concerned with the bodily structure. The discipline of anatomy is divided into macroscopic and microscopic anatomy. • Gross Anatomy (Macroscopic Anatomy) is the study of systemic, body surface, regions, and sections. It studies organs and their relationship to one another. ➢In regional anatomy: all the structures (muscles, bones, blood vessels, nerves, etc.) in a particular region of the body, such as the abdomen or leg, are examined at the same time. ➢In systemic anatomy: body structure is studied system by system. For example, when studying the cardiovascular system, you would examine the heart and the blood vessels of the entire body. ➢Another subdivision of gross anatomy is surface anatomy, the study of internal structures as they relate to the overlying skin surface. Anatomy: • Microscopic Anatomy studies the cells and tissues. Cytology is the study of cells and Histology is the study of tissues. • Developmental Anatomy This is the branch of anatomy which starts with the study of the structural changes right from the fertilization to the maturity stage. In this we keep a closer look on how an individual’s structures change with time (Embryology). Physiology • Is the science of the mechanical, physical, and biochemical functions of normal humans or human tissues or organs or cells. The principal level of focus of physiology is at the level of organs and systems. • Physiology often focuses on events at the cellular or molecular level. This is because the body's abilities depend on those of its individual cells, and cells' abilities ultimately depend on the chemical reactions that go on within them. • Physiology also rests on principles of physics, which help to explain electrical currents, blood pressure, and the way muscles use bones to cause body movements, among other things. • Is also the study of diseases Subdivisions of physiology include: • Pathophysiology • Exercise Physiology • Neurophysiology • Endocrinology • Cardiovascular Physiology • Cell Physiology • Nutritional Physiology • Respiratory Physiology • Physiological Diet Central Themes in Physiology 1. Function is based on structure: this key concept is called the Principle of Complementarity of structure and function 2. Homeostasis – Maintenance of a constant internal environment – Homeostasis relies on feedback mechanisms Complementarity of structure and function Emphasize structural characterization contributing to that function Levels of Organization • • • • • • Chemical (atoms, molecules) Cellular Tissue Organ System Organism (Human) The interrelationship among body organ systems The systems of the human body are the – integumentary – skeletal – muscular – nervous – endocrine – cardiovascular – lymphatic – respiratory – urinary – digestive – reproductive The body’s organ systems and their functions The body’s organ systems and their functions The body’s organ systems and their functions The body’s organ systems and their functions The major functional characteristic of the human body All living things have certain characteristics that distinguish them from non-living things – Metabolism – Responsiveness – Movement – Growth – Differentiation / Organization – Digestion – Reproduction Basic Life Processes • Metabolism is the sum of all chemical processes that occur in the body, including catabolism and anabolism. • Digestion and Excretion, Digestion refers to the breakdown of food into smaller components that can be absorbed into the bloodstream. Excretion is a process in which metabolic waste is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. • Responsiveness is the ability to detect and respond to changes in the external or internal environment. • Movement includes motion of the whole body, individual organs, single cells, or even organelles inside cells. Basic Life Processes • Growth refers to an increase in size and complexity, due to an increase in the number of cells, size of cells, or both. • Differentiation is the change in a cell from an unspecialized state to a specialized state. • Reproduction refers either to the formation of new cells for growth, repair, or replacement, or the production of a new individual. Survival Needs • Nutrients. Nutrients, taken in via the diet, contain the chemical substances used for energy and cell building. Most plant-derived foods are rich in carbohydrates, vitamins, and minerals, whereas most animal foods are richer in proteins and fats. • Oxygen. All the nutrients in the world are useless unless oxygen is also available. Because the 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. The cooperative efforts of the respiratory and cardiovascular systems make oxygen available to the blood and body cells. Survival Needs • Water. Water accounts for 50-60% of our body weight and is the single most abundant chemical substance in the body. It provides the watery environment necessary for chemical reactions and the fluid base for body secretions and excretions. We obtain water from ingested foods and liquids. We lose it form the body by evaporation from the lungs and skin and in body excretions. • Normal body temperature. If chemical reactions are to continue at lifesustaining 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, chemical reactions occur at a frantic pace and body systems stop functioning. At either extreme, death occurs. The activity of the muscular system generates most body heat. Survival Needs • Appropriate atmospheric pressure. Atmospheric pressure is 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. Homeostasis • Homeostasis is a condition of equilibrium in the body’s internal environment produced by continual interplay of all the body’s regulatory processes. • Maintenance of a constant internal environment, despite changes in the external environment. • Maintaining the internal environment within physiological limits. – e.g. blood glucose level is kept within narrow range 70-110mg/100ml https://www.youtube.com/watch?v=DZDqIoKzvEg Homeostasis • Homeostasis is continually being disrupted by: – external stimuli • intense heat, cold, lack of oxygen – internal stimuli • psychological stresses • exercise Components of Homeostasis (Approaches) (Exits) • Receptors – change in variable • Control Centre – compare to set-point • Effectors – undo the change invariable Homeostatic Control Systems • Feedforward - term used for responses made in anticipation of a change • Feedback - refers to responses made after change has been detected – Types of feedback systems • Negative • Positive Feedback Loops: Types • Negative feedback loop – original stimulus reversed – most feedback systems in the body are negative – used for conditions that need frequent adjustment • Positive feedback loop – original stimulus intensified – seen during normal childbirth Negative feedback loop Positive feedback loop Torn blood vessel stimulates release of clotting factor Anatomical terms describe body directions, regions, and planes Learning outcome: • Describe the anatomical position. • Use correct anatomical terms to describe body directions, regions, and body planes or sections. Anatomical terms describe body directions, regions, and planes • To describe body parts and position accurately, we need an initial reference point, and we must indicate direction. The anatomical reference point is a standard body position called the anatomical position. • Directional terms allow us to explain where one body structure is in relation to another. For example, we could describe the relationship between the ears and the nose by stating, "The ears are located on each side of the head to the right and left of the nose." Using anatomical terminology, this becomes "The ears are lateral to the nose.“ • Using anatomical terms saves words and is less ambiguous Regional Terms • The two fundamental divisions of our body are its Axial and Appendicular parts. • The axial part, which makes up the main axis of our body, includes the head, neck, and trunk. • The appendicular part consists of the appendages, or limbs, which are attached to the body's axis. • Regional terms used to designate specific areas within these major body divisions Regional terms used to designate specific body areas. Directional terms Body Planes and Sections • For anatomical studies, the body is often cut, or sectioned, along a flat surface called a plane. • The most frequently used body planes are sagittal, frontal, and transverse planes. • A Sagittal Plane is a vertical plane that divides the body into right and left parts. • A sagittal plane that lies exactly in the midline is The Median Plane, or Midsagittal Plane. All other sagittal planes, offset from the midline, are Parasagittal Planes. • Frontal planes, like sagittal planes, lie vertically. Frontal planes, however, divide the body into anterior and posterior parts. A frontal plane is also called a Coronal Plane • A transverse, or horizontal, plane runs horizontally from right to left, dividing the body into superior and inferior parts. Of course, many different transverse planes exist, at every possible level from head to foot. A transverse section is also called A Cross Section. • Oblique sections are cuts made diagonally between the horizontal and the vertical planes. Because oblique sections are often confusing and difficult to interpret, they are rarely used. Body Planes and Sections Image below includes examples of magnetic resonance imaging (MRI) scans that correspond to the three sections shown in the figure. Clinically, the ability to interpret sections made through the body, especially transverse sections, is important. Additionally, certain medical imaging devices produce sectional images rather than threedimensional images Many internal organs lie in membrane-lined body cavities Dorsal Body Cavity • The dorsal body cavity, which protects the fragile nervous system organs, has two subdivisions. • The cranial cavity, in the skull, encases the brain. • The vertebral, or spinal, cavity, which runs within the bony vertebral column, encloses the delicate spinal cord. • The spinal cord is essentially a continuation of the brain, and the cranial and spinal cavities are continuous with one another. Both the brain and the spinal cord are covered by membranes called meninges. Many internal organs lie in membrane-lined body cavities Ventral Body Cavity • The more anterior and larger of the closed body cavities is the ventral body cavity. • Like the dorsal cavity, it has two major subdivisions, the thoracic cavity and the abdominopelvic cavity. • The ventral body cavity houses internal organs collectively called the viscera or visceral organs. • The superior subdivision, the thoracic cavity is surrounded by the ribs and muscles of the chest. • The thoracic cavity is further subdivided into lateral pleural cavities each enveloping a lung, and the medial mediastinum. • The mediastinum contains the pericardial cavity, which encloses the heart, and it also surrounds the remaining thoracic organs (esophagus, trachea, and others). Ventral Body Cavity • The thoracic cavity is separated from the more inferior abdominopelvic cavity by the diaphragm. • The abdominopelvic cavity, as its name suggests, has two parts. However, these regions are not physically separated by a muscular or membrane wall. Its superior portion, the abdominal cavity, contains the stomach, intestines, spleen, liver, and other organs. • The inferior part, the pelvic cavity, lies in the bony pelvis and contains the urinary bladder, some reproductive organs, and the rectum. • The abdominal and pelvic cavities are not aligned with each other. Instead, the bowl-shaped pelvis tips away from the perpendicular. Dorsal and ventral body cavities and their subdivisions Membranes in the Ventral Body Cavity • The walls of the ventral body cavity and the outer surfaces of the organs it contains are covered by a thin, doublelayered membrane, the serosa or serous membrane. Which covers the heart. • Likewise, the parietal pleurae line the walls of the thoracic cavity, and the visceral pleurae cover the lungs. • The parietal peritoneum is associated with the walls of the abdominopelvic cavity, while the visceral peritoneum covers most of the organs within that cavity. Abdominopelvic Regions and Quadrants • A transverse and a median plane pass through the umbilicus at right angles. • The four resulting quadrants are named according to their positions from the subject's point of view: 1. 2. 3. 4. Right upper quadrant (RUQ), Left upper quadrant (LUQ), Right lower quadrant (RLQ), Left lower quadrant (LLQ). The nine abdominopelvic regions References and Further Reading • Elaine N. Marieb and Katja N. Hoehn (2019). Human Anatomy and Physiology. 11th Edition. Pearson Education. Chapter 1