The Human Body: An Orientation

1. 1 P A R T A The Human Body: An Orientation

2. Overview of Anatomy and Physiology • Anatomy – (Greek – to cut up) - the study of the structure of body parts and their relationships to one another • Gross or macroscopic • Microscopic • Developmental • Physiology – (Greek – study of nature) - the study of the function of the body’s structural machinery; explains physical & chemical processes that direct body activities

3. Gross Anatomy • Regional – all structures in one part of the body (such as the abdomen or leg) • Systemic – gross anatomy of the body studied by system • Surface – study of internal structures as they relate to the overlying skin

4. Microscopic Anatomy • Cytology – study of the cell • Histology – study of tissues Developmental Anatomy • Traces structural changes throughout life • Embryology – study of developmental changes of the body before birth

5. Specialized Branches of Anatomy • Pathological anatomy – study of structural changes caused by disease • Radiographic anatomy – study of internal structures visualized by specialized scanning procedures such as X-ray, MRI, and CT scans • Molecular biology – study of anatomical structures at a subcellular level

6. Physiology • Considers the operation of specific organ systems • Renal – kidney function • Neurophysiology – workings of the nervous system • Cardiovascular – operation of the heart and blood vessels • Focuses on the functions of the body, often at the cellular or molecular level

7. Understanding physiology also requires a knowledge of physics, which explains • electrical currents • blood pressure • the way muscle uses bone for movement

8. Principle of Complementarity • Function always reflects structure • What a structure can do depends on its specific form • Core theme - Structure (anatomy) determines what functions (physiology) can take place; if structure changes, the function must also change

9. 6 Levels of Structural Organization • Chemical – atoms combine to form molecules which combine to form cells • Cellular – smallest unit of life; human composed of 60-100 trillion cells; combine to form tissues • Tissue – groups of cells that perform a common function; four types = epithelial, connective, muscular, & nervous • Organ – composed of two or more tissue types that perform a specific function; most contain all 4 tissue types • Organ system – group of organs that cooperate to accomplish a common purpose; ex. circulatory system, digestive system, etc. • Organismal – highest level of structural organization; all systems of body working together

10. Molecules Atoms 1 Chemical level Atoms combine to form molecules. Levels of Structural Organization Figure 1.1

11. Smooth muscle cell Molecules Cellular level Cells are made up of molecules. 2 Atoms 1 Chemical level Atoms combine to form molecules. Figure 1.1

12. Smooth muscle cell Molecules Cellular level Cells are made up of molecules. 2 Atoms 1 Chemical level Atoms combine to form molecules. Smooth muscle tissue 3 Tissue level Tissues consist of similar types of cells. Figure 1.1

13. Smooth muscle cell Molecules Cellular level Cells are made up of molecules. 2 Atoms 1 Chemical level Atoms combine to form molecules. Smooth muscle tissue 3 Tissue level Tissues consist of similar types of cells. Epithelial tissue Smooth muscle tissue Blood vessel (organ) Connective tissue 4 Organ level Organs are made up of different types of tissues. Figure 1.1

14. Smooth muscle cell Molecules Cellular level Cells are made up of molecules. 2 Atoms 1 Chemical level Atoms combine to form molecules. Smooth muscle tissue 3 Tissue level Tissues consist of similar types of cells. Heart Cardiovascular system Blood vessels Epithelial tissue Smooth muscle tissue Blood vessel (organ) Connective tissue 4 Organ level Organs are made up of different types of tissues. 5 Organ system level Organ systems consist of different organs that work together closely. Figure 1.1

15. Smooth muscle cell Molecules Cellular level Cells are made up of molecules. 2 Atoms 1 Chemical level Atoms combine to form molecules. Smooth muscle tissue 3 Tissue level Tissues consist of similar types of cells. Heart Cardiovascular system Blood vessels Epithelial tissue Smooth muscle tissue Blood vessel (organ) 6 Organismal level The human organism is made up of many organ systems. Connective tissue 4 Organ level Organs are made up of different types of tissues. 5 Organ system level Organ systems consist of different organs that work together closely. Figure 1.1

16. 10 Necessary Life Functions • Maintaining boundaries – the internal environment remains distinct from the external environment • Cellular level – accomplished by plasma membranes • Organismal level – accomplished by the skin • Organization – structure & functions is determined by genetics • Movement – locomotion, propulsion (peristalsis), blood, breathing, molecules, and contractility

17. Responsiveness – ability to monitor internal or external conditions and react to changes • Digestion – breakdown of ingested foodstuffs; process by which complex substances are converted to simpler forms so that they can be absorbed through intestinal wall & transported by blood • Metabolism – all the chemical reactions that occur in the body; releases energy, creates body heat, enables cells to synthesize & secrete molecules • Excretion – removal of wastes produced by metabolism

18. Reproduction – cellular and organismal levels • Cellular – an original cell divides and produces two identical daughter cells • Organismal – sperm and egg unite to make a whole new person • Growth – increase in size of a body part or of the organism • Differentiation – result in structurally and functionally distinct organs

19. Survival Needs • Nutrients – needed for energy and cell building • Oxygen – 20% of air; needed for release of energy during cellular respiration and for metabolic reactions • Water – min. 60% of body weight; provides the necessary environment for chemical reactions • Normal body temperature – necessary for chemical reactions to occur at life-sustaining rates • Atmospheric pressure – required for proper breathing and gas exchange in the lungs

20. Homeostasis • Homeostasis – ability to maintain a relatively stable internal environment in an ever-changing outside world • The internal environment of the body is in a dynamic state of equilibrium • Chemical, thermal, and neural factors interact to maintain homeostasis; necessary for survival and good health; its loss results in illness or disease

21. Homeostatic Control Mechanisms • Variables produce a change in the body • The three interdependent components of control mechanisms: • Receptor (sensor) – responds to a stimuli (environmental change) by sending information to the control center • Control center – determines the set point at which the variable is maintained; usually consists of brain, spinal cord, or endocrine gland; assesses multiple stimuli, determines deviations from standard set points, and produces a response by increasing or decreasing the activity of the effector • Effector – muscles or glands; provides the means to respond to stimuli

22. Variable (in homeostasis) Homeostatic Control Mechanisms Figure 1.4

23. Stimulus: Produces change in variable 1 Imbalance Variable (in homeostasis) Imbalance Figure 1.4

24. Receptor (sensor) 2 Change detected by receptor Stimulus: Produces change in variable 1 Imbalance Variable (in homeostasis) Imbalance Figure 1.4

25. 3 Input: Information sent along afferent pathway to Control center Receptor (sensor) 2 Change detected by receptor Stimulus: Produces change in variable 1 Imbalance Variable (in homeostasis) Imbalance Figure 1.4

26. 3 Input: Information sent along afferent pathway to Control center 4 Output: Information sent along efferent pathway to Receptor (sensor) Effector 2 Change detected by receptor Stimulus: Produces change in variable 1 Imbalance Variable (in homeostasis) Imbalance Figure 1.4

27. 3 Input: Information sent along afferent pathway to Control center 4 Output: Information sent along efferent pathway to Receptor (sensor) Effector 2 Change detected by receptor 5 Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis Stimulus: Produces change in variable 1 Variable (in homeostasis) Homeostatic Control Mechanisms Figure 1.4

28. Negative Feedback • In negative feedback systems, the output shuts off the original stimulus • Most control systems involve negative feedback systems which act to reduce or stop the initial stimulus; ex. maintenance of body temperature - antagonistic actions – opposite actions; allow for fine tuning of homeostatic conditions • Example: Regulation of room temperature

29. Signalwire turns heater off Control center (thermostat) Set point Receptor-sensor (thermometer in Thermostat) Heater off Effector (heater) Response; temperature drops Stimulus: rising room temperature Imbalance Balance Response; temperature rises Stimulus: dropping room temperature Imbalance Heater on Set point Effector (heater) Receptor-sensor (thermometer in Thermostat) Signal wire turns heater on Control center (thermostat) Figure 1.5

30. Balance Figure 1.5

31. Stimulus: rising room temperature Imbalance Balance Imbalance Figure 1.5

32. Set point Receptor-sensor (thermometer In thermostat) Stimulus: rising room temperature Imbalance Balance Imbalance Figure 1.5

33. Control center (thermostat) Set point Receptor-sensor (thermometer In thermostat) Stimulus: rising room temperature Imbalance Balance Imbalance Figure 1.5

34. Signal wire turns heater off Control center (thermostat) Set point Stimulus: dropping room temperature Receptor-sensor (thermometer In thermostat) Heater off Effector (heater) Stimulus: rising room temperature Response; temperature drops Balance Figure 1.5

35. Imbalance Balance Stimulus: dropping room temperature Imbalance Figure 1.5

36. Imbalance Balance Stimulus: dropping room temperature Imbalance Set point Receptor-sensor (thermometer in Thermostat) Figure 1.5

37. Imbalance Balance Stimulus: dropping room temperature Imbalance Set point Receptor-sensor (thermometer in Thermostat) Control center (thermostat) Figure 1.5

38. Imbalance Balance Stimulus: dropping room temperature Imbalance Heater on Set point Effector (heater) Receptor-sensor (thermometer in Thermostat) Signal wire turns heater on Control center (thermostat) Figure 1.5

39. Balance Response; temperature rises Stimulus: dropping room temperature Heater on Set point Effector (heater) Receptor-sensor (thermometer in Thermostat) Signal wire turns heater on Control center (thermostat) Figure 1.5

40. Signalwire turns heater off Control center (thermostat) Set point Receptor-sensor (thermometer in Thermostat) Heater off Effector (heater) Response; temperature drops Stimulus: rising room temperature Imbalance Balance Response; temperature rises Stimulus: dropping room temperature Imbalance Heater on Set point Effector (heater) Receptor-sensor (thermometer in Thermostat) Signal wire turns heater on Control center (thermostat) Figure 1.5

41. Positive Feedback • In positive feedback systems, the output enhances or exaggerates the original stimulus • Rare in humans; works against homeostasis • Example: Regulation of blood clotting • Ex. Oxytocin during labor stimulated by pressure on cervix; causes greater uterine contractions & more pressure on cervix Figure 1.6

42. 1 Break or tear in blood vessel wall Feedback cycle initiated Figure 1.6

43. Break or tear in blood vessel wall 1 Feedback cycle initiated 2 Clotting occurs as platelets adhere to site and release chemicals Figure 1.6

44. Break or tear in blood vessel wall 1 Feedback cycle initiated 2 Clotting occurs as platelets adhere to site and release chemicals 3 Released chemicals attract more platelets Figure 1.6

45. Break or tear in blood vessel wall 1 Feedback cycle initiated 2 Clotting occurs as platelets adhere to site and release chemicals 3 Released chemicals attract more platelets 4 Clotting proceeds; newly forming clot grows Figure 1.6

46. Positive Feedback System Break or tear in blood vessel wall 1 Feedback cycle initiated Feedback cycle ends after clot seals break 2 Clotting occurs as platelets adhere to site and release chemicals 3 Released chemicals attract more platelets 4 Clotting proceeds; newly forming clot grows Figure 1.6

47. Homeostatic Imbalance • Disturbance of homeostasis or the body’s normal equilibrium • Overwhelming the usual negative feedback mechanisms allows destructive positive feedback mechanisms to take over

48. Directional Terms • Superior and inferior – toward and away from the head, respectively • Anterior and posterior – toward the front and back of the body • Medial, lateral, and intermediate – toward the midline, away from the midline, and between a more medial and lateral structure • Proximal and distal – closer to and farther from the origin of the body part • Superficial and deep – toward and away from the body surface

49. Directional Terms Table 1.1a

50. Directional Terms Table 1.1b