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1.1: Introduction

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    Introduction

    Anatomy is the study of biological structures. Biological structures may be examined and studied at levels visible to the human eye, gross anatomy, or at levels too small for the human eye to see, microscopic anatomy. Microscopic anatomy requires the use of microscopes and includes the study of cells, cytology, and the study of tissues, histology.

    The structure of a human can be broken down based on levels of organization:

    1. human
    2. organ systems
    3. organs
    4. tissues
    5. cells
    6. molecules
    7. atoms

    Each level of structural organization is composed of the smaller levels below it. For example: cells are composed of molecules, tissues are composed of cells, and humans are composed of organ systems. In fact, humans are composed of eleven (11) organ systems:

    • cardiovascular/circulatory system - transports substances (e.g. oxygen [O2], carbon dioxide [CO2], glucose, hormones) throughout the body
    • integumentary system – provides protecting coverings to the body
    • digestive system – processes food to provide nutrients (energy, biological building blocks, and vitamins)
    • muscular system – provides movement to the body
    • endocrine system – produces hormones that signal cells, tissues, and organs throughout the body
    • lymphatic system - cleanses and returns tissue fluid to the cardiovascular/circulatory system and provides adaptive immune responses
    • nervous system – provides ability to interact with and interpret the environment (both the inside and outside environments)
    • skeletal system – provides framework for movement and protection of the organs of the body
    • reproductive systems (male and female) – produces offspring
    • respiratory system – exchanges oxygen (O2) for carbon dioxide (CO2)
    • urinary/excretory system – filters blood and discards waste products (wastes from metabolism, foreign substances, etc.)

    This illustration shows eight silhouettes of a human female, each showing the components of a different organ system. The integumentary system encloses internal body structures and is the site of many sensory receptors. The integumentary system includes the hair, skin, and nails. The skeletal system supports the body and, along with the muscular system, enables movement. The skeletal system includes cartilage, such as that at the tip of the nose, as well as the bones and joints. The muscular system enables movement, along with the skeletal system, but also helps to maintain body temperature. The muscular system includes skeletal muscles, as well as tendons that connect skeletal muscles to bones. The nervous system detects and processes sensory information and activates bodily responses. The nervous system includes the brain, spinal cord, and peripheral nerves, such as those located in the limbs. The endocrine system secretes hormones and regulates bodily processes. The endocrine system includes the pituitary gland in the brain, the thyroid gland in the throat, the pancreas in the abdomen, the adrenal glands on top of the kidneys, and the testes in the scrotum of males as well as the ovaries in the pelvic region of females. The cardiovascular system delivers oxygen and nutrients to the tissues as well as equalizes temperature in the body. The cardiovascular system includes the heart and blood vessels.

    The lymphatic system returns fluid to the blood and defends against pathogens. The lymphatic system includes the thymus in the chest, the spleen in the abdomen, the lymphatic vessels that spread throughout the body, and the lymph nodes distributed along the lymphatic vessels. The respiratory system removes carbon dioxide from the body and delivers oxygen to the blood. The respiratory system includes the nasal passages, the trachea, and the lungs. The digestive system processes food for use by the body and removes wastes from undigested food. The digestive system includes the stomach, the liver, the gall bladder (connected to the liver), the large intestine, and the small intestine. The urinary system controls water balance in the body and removes and excretes waste from the blood. The urinary system includes the kidneys and the urinary bladder. The reproductive system of males and females produce sex hormones and gametes. The male reproductive system is specialized to deliver gametes to the female while the female reproductive system is specialized to support the embryo and fetus until birth and produce milk for the infant after birth. The male reproductive system includes the two testes within the scrotum as well as the epididymis which wraps around each testis. The female reproductive system includes the mammary glands within the breasts and the ovaries and uterus within the pelvic cavity.

    There is overlap among these body systems with organs belonging to more than one organ system. For example, the ovaries are organs of the female reproductive system but they also produce hormones and are therefore considered to be endocrine organs also. There is also extensive interaction among these body systems. For example, the respiratory system brings oxygen (O2) into the body and removes carbon dioxide (CO2) from the body and works closely with the cardiovascular/circulatory system that takes O2 from the respiratory system and transports it to body cells while removing CO2 from body cells and transporting it to the respiratory system for removal.

    Physiology is the study of biological functions and interactions and is often closely related to the anatomy since in biology, structure dictates function. Therefore, to best understand how a living thing functions (physiology), it is necessary to understand its structure (anatomy). Physiology may be studied from the molecular level to the organism level.

    Attributions

    This page titled 1.1: Introduction is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.

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