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Human Anatomy & Physiology

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Contents

Answers to Chapter Review Questions....................................................205-224

Chapter One

Anatomy: Anatomy can be divided into gross (macroscopic) anatomy and microscopic anatomy

1.1 Branches of Anatomy and Physiology

1.1.1 Gross Anatomy

In gross anatomy we study relatively large structures, such as the heart, kidney, and lungs, without the aid of a microscope. There are many different branches of gross anatomy:

1. Surface anatomy is the study of general form and superficial markings. 2. Regional anatomy focuses on anatomical organization of specific areas of the body. 3. Systemic anatomy is the study of the structure of organ systems, such as the digestive system. 4. Developmental anatomy deals with the study of the changes in forms that occur between conception and physical maturity. 5. Clinical anatomy focuses on different areas of specialties in clinical practice-e.g., medical anatomy, radiographic anatomy, and surgical anatomy.

1.1.2 Microscopic Anatomy

1. Cytology is the study of the internal structure of individual cells with the aid of microscopes. 2. Histology is the branch of anatomy that deals with the study of tissues.

1.1.3 Physiology

The study of the functions of the human body

1. Cell physiology is the study of the functions of cells. 2. Special physiology is the study of the physiology of special organs. 3. Systemic physiology is the study of the functioning of specific organ systems. 4. Pathological physiology is the study of the effects of diseases on organs or organ systems' functions.

1.1.4 Levels of Organization

1. The chemical (or molecular) level: atoms and molecules 2. The cellular level: molecules interacting to form organelles 3. The tissue level: groups of cells working together to perform one or more specific functions 4. The organ level: two or more tissues working in combination to perform several functions 5. The organ system level: organs interacting in organ systems 6. The organism level: an organism, such as a human

1.1.5 Necessary Life Functions

1. Maintaining Boundaries: All the cells in the body are surrounded by selectively permeable membranes keeping unwanted materials out.

2. Movement: All activities in the body facilitated by the muscular system, such as blood circulation or propelling food through the digestive system. Movement is carried out by entire organisms, organs, tissues, cells, or organelles.

3. Responsiveness: Ability to sense changes in the environment and respond to them accordingly. The organism detects stimulus, and the effectors respond to the stimulus.

4. Metabolism: It involves all the chemical reactions occurring in the body cells. It includes breaking down substances (catabolism) and synthesizing complex substances from simpler ones (anabolism). Metabolism depends on the digestive and respiratory systems to make oxygen and nutrients available and on the cardiovascular system, which transports them throughout the body.

5. Growth: Increase in the size of a body part or an organism. For true growth to occur in cells, constructive activities in the cells must supersede the destructive activities.

6. Reproduction: In cellular reproduction, the parent cell divides to form identical two daughter cells that may be used for growth in multicellular organisms.

7. Excretion: The process of removing wastes, which may be carried out by the lungs, the digestive system, the urinary system, or the integumentary system.

8. Differentiation: Specialization of embryonic tissues into different body tissues with limited capabilities. This occurs as different set of genes are switched off in the chromosomes of different cells.

1.1.6 Homeostasis

Homeostasis is very important to an organism. When homeostasis fails, it leads to illness or even death. Two general mechanisms are involved in homeostatic regulation: autoregulation and extrinsic regulation.

1. Autoregulation (intrinsic regulation): Cells, tissues, and organ system have the ability to regulate their functions automatically in response to changes in the environment; e.g., when the [O.sub.2] level declines in a tissue, the cells release chemicals to dilate local blood vessels. 2. Extrinsic regulation results from the activities of the nervous system or endocrine system; for instance, after exercise, the nervous system increases your heart rate in order for blood to circulate faster.

A homeostatic regulatory mechanism consists of three parts:

1. Receptor is a sensor that is sensitive to a particular environmental change or stimulus. 2. Control center receives and processes the information supplied by the receptor. 3. Effector is a cell or organ that responds to the commands of the control center. Its activity either opposes or enhances the stimulus.

1.1.7 The Role of Negative Feedback

Most activities in our body are regulated by negative feedback mechanisms. An important example is the control of body temperature, a process called thermoregulation. The following steps are involved:

A stimulus produces a response that opposes or negates the original stimulus-e.g., the temperature changes. A Receptor senses the stimulus (temperature sensors in skin and hypothalamus). Control center (in this case the thermoregulatory center in the brain) is affected, then sends commands to

Effectors: Sweat glands in the skin increase secretions, and blood vessels in the skin dilate.

Response: With increased heat loss, body temperature drops and normal temperature is restored.

1.1.8 The Role of Positive Feedback

A positive feedback mechanism occurs when the stimulus produces a reaction that exaggerates or enhances the effect of the stimulus rather than reverses it. Steps involved in the positive feedback in blood clotting are as follows:

1. A break in a blood vessel wall causes bleeding. 2. Damaged cells release chemicals. 3. Clotting begins. 4. Additional chemicals are released (causing clotting to accelerate). 5. A blood clot plugs the break in the vessel wall, and bleeding stops.

"Positive feedback is important in accelerating processes that must proceed to completion rapidly. Think of a positive feedback as a domino effect-once the domino begins to fall, the chain reaction causes each successive domino to fall until completion." (Instructor's Guide Resource Guide by Lucia Tranel and Alice Mills-Fundamentals of Anatomy & Physiology by Frederic H Martini, Third Edition)

1.1.9 Anatomical Position

A person is in an anatomical position when the following conditions are fulfilled:

1. Erect 2. Facing observer 3. Eyes forward 4. Arms at sides 5. Palms forward 6. Feet flat on the floor 7. Big toes together 8. Thumbs point away from the body 9. "Right" and "left" refer to the...