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This chapter focuses on the structural organization of the body, specifically the different types of cells and their functions. It explores the cell membrane, nucleus, chromosomes, cytoplasm, mitochondria, endoplasmic reticulum, metabolism, karyotype, and amniocentesis.
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Chapter 2:Terms Pertaining to the Body as a Whole Tri-State Business Institute MD000 Medical Terminology 1 Micheal H. McCabe, EMT-P
Structural Organization of the Body: • The cell is the fundamental unit of all living things. • All cells have a similar structure. • Cells are everywhere in the body – every organ and tissue is composed of cells. • The study of cells is called cytology. The study of tissues is called histology.
Parts of the Cell: • [1] Cell Membrane – surrounds and protects the cell. Also Regulates what passes into and out of the cell. • [2] Nucleus – is the control center of the cell. Genetic material in the nucleus determines the structure and function of the cell and controls reproduction.
Parts of the Cell: • [3] Chromosomes are rod-like structures within the nucleus. Most human cells contain 23 paired chromosomes that comprise the human genome. • Chromosomes contain regions called genes. Each gene is built up of DNA. The DNA serves as a chemical “program” that directs the function of the cell.
Parts of the Cell: • [4] Cytoplasm is all the material outside the nucleus and enclosed by the cell membrane. It includes intracellular fluid as well as discrete structures like the mitochondria[a], endoplasmic reticulum[b], and ribosomes.
Mitochondria: • Small, sausage-shaped bodies found in the cytoplasm. • Mitochondria are the “power-plants” within the cell that produce energy by combining food with oxygen. • This chemical process is called catabolism.
Endoplasmic Reticulum: • Is a network of canals (reticulum) within the cell. • The endoplasmic reticulum (ER) contains very small structures called ribosomes that manufacture protein. • This chemical process is called anabolism.
Metabolism: • Metabolism is the total of the chemical processes within the cell. • Metabolism includes catabolism and anabolism. • If a person has a “fast” metabolism, nutrients are used up quickly and energy is released. • If a person has a “slow” metabolism, nutrients are used slowly and fat accumulates in the cells.
Karyotype: • A karyotype is a photographic “map” of the chromosomes. • The chromosomes are treated with chemicals so that light and dark areas are visible. • An electron microscope is used to visualize and photograph the chromosomes.
Amniocentisis: • This procedure is undertaken to check an unborn baby for chromosomal abnormalities. • A needle is used to aspirate a quantity of cells from the amniotic sac. • A karyotype is created from the aspirated cells. • This is a prenatal test frequently used to diagnose Down’s Syndrome.
Study Section 1: • Anabolism – the process of building up complex materials (proteins) from simple materials. • Catabolism – the process of breaking down complex materials (foods) to form simpler substances and release energy.
Study Section 1: • Cell Membrane – Structure surrounding and protecting the cell. It determines what enters and leaves the cell. • Chromosomes – rod-shaped structures in the nucleus that contain regions of DNA called genes. There are 46 chromosomes (23 pairs) in most human cells. • Cytoplasm – all the material that is outside the nucleus yet contained within the cell membrane.
Study Section 1: • DNA – deoxyribonucleic acid; chemical found in each chromosome. Arranged like a sequence of recipes in code, it directs the activities of the cell. • Endoplasmic Reticulum – Structures (canals) within the cytoplasm. Site in which large proteins are made from smaller pieces (amino acids.)
Study Section 1: • Genes – regions of DNA within each chromosome. • Karyotype – Picture of chromosomes in the nucleus of a cell. The chromosomes are arranged in numerical order to determine their number and structure.
Study Section 1: • Metabolism – The total of the chemical processes in a cell. It includes both catabolism and anabolism. • Mitochondria – Sausage-shaped structures in the cytoplasm in which foods are burned to release energy; “power plants.”
Study Section 1: • Nucleus – Control center of the cell. It contains chromosomes and directs the activities of the cell.
Differences in Cells: • Cells throughout the body are specialized to perform particular tasks. • A group of similar cells working together to do a specific job is called a tissue. • A specialist who studies tissues is called a histologist.
Some Types of Cells: • Muscle Cells – are long, slender, and contain contractile fibers that allow them to shorten their length. • Epithelial Cells – are specialized cells that form protective membranes like the skin. • Nerve Cells – are very long and have various fibrous extensions that aid its job of carrying impulses. • Fat Cells – contain large empty spaces for fat storage.
Epithelial Tissue: • Epithelial Tissue – is located throughout the body and forms the lining of internal organs, makes up exocrine and endocrine glands, and forms the outer surface of the skin covering the body. The word epithelial was originally used to describe the tissue above the breast nipple. Now it is used to describe the tissues that cover the outside of the body and line the internal cavities.
Muscle Tissue: • Voluntary muscle is found attached to the skeleton. It allows voluntary movement under conscious control. • Involuntary muscle (smooth muscle) is found in the walls of the blood vessels, intestines, and hollow organs of the body. This movement is not under conscious control. • Cardiac Muscle is found only in the walls of the heart (myocardium) and is specialized in that it will contract automatically – independent of nervous system action. This property is called automaticity.
Connective Tissue: • Connective tissue is the most common and the most diverse of all body tissues. • Examples are fat (adipose tissue), bone, cartilage, and blood. • Connective tissue is characterized by relatively few cells that create non-cellular structures known as matrix.
Nerve Tissue: • Nerve tissue conducts impulses all over the body. • Nerve cells have specialized extensions called axons and dendrites that serve as specialized communication lines. • The Axon carries messages (impulses) away from the body of the nerve cell. It serves as a transmitter. Each nerve cell has only one axon. • Dendrites carry messages (impulses) towards the body of the cells. They serve as receivers. Each nerve cell can have many dendrites.
Organs: • Organs are structures composed of several kinds of tissue. • For example, the stomach is composed of muscle tissue, nerve tissue, glandular epithelial tissue, and connective tissue. • The medical term for internal organs is viscera (singular form: viscus) • Examples of abdominal viscera include the liver, stomach, pancreas, intestines, spleen, and gallbladder.
Systems: • Systems are groups of organs working together to perform complex functions. • Different books and authors group the organ systems differently. • Example: This book groups the body into ten body systems. The A&P class groups the body into 15 systems.
Digestive System: • Function is to digest food, absorb nutrients into the bloodstream, and eliminate solid waste. • Organs include the mouth, pharynx, esophagus, stomach, intestines, liver, gallbladder, and pancreas.
Urinary System: • Also called the excretory system. • Function is to eliminate metabolic waste, maintain the fluid balance of the body, regulate electrolyte levels, and govern the acid/base balance. • Organs include the kidneys, ureters, bladder, and urethra.
Respiratory System: • Function is to bring oxygen into the bloodstream and eliminate carbon dioxide. Also helps regulate the acid/base balance. • Organs include the nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
Reproductive System: • Function is to enable reproduction of the entire organism and to help perpetuate the species. • Organs differ somewhat between males and females. • Male organs include the testes and assorted tubes, urethra, prostate gland, and penis. • Female organs include the ovaries, fallopian tubes, uterus, vagina, and mammary glands.
Endocrine: • Function is of a chemical communication system that regulates function and metabolism at a cellular level. • Organs include the pituitary gland, thyroid gland, sex glands (gonads), adrenal glands, parathyroid gland, thymus, and the pancreas.
Nervous System: • Function is complex – includes command, control, and communication throughout the entire body. • Organs include the brain, spinal cord, cranial nerves, spinal nerves, and other collections of nerve structures.
Circulatory System: • Functions as a transportation system – used to move oxygen, nutrients, waste products, carbon dioxide, chemicals, hormones, and immune system components throughout the body. • Organs include the heart, blood vessels, lymphatic vessels and nodes, blood, lymph, spleen, and thymus gland. • One of the more complex systems we will discuss.
Muscular System: • Function is to enable movement: skeletal muscles move the body itself; smooth muscles move substances within the body; cardiac muscle enables operation of the circulatory system. • Organs include more than 600 muscles and tendons.
Skeletal System: • Provides supporting framework for the body; also protects internal organs and provides for movement via its articulations. • Includes more than 200 bones plus ligaments, cartilage, and joint structures.
Skin and Sense Organs: • The skin provides an overall covering for the body. • Accessory organs of the skin include hair and nails. • General sense organs are embedded within the skin. • Special sense organs are complex independent structures.
Study Section 2: • Adipose tissue – collection of fat cells. • Cartilage – flexible connective tissue attached to bones at joints. • Epithelial Cell – skin cells that cover the external body surfaces and line the internal surfaces of organs. • Histologist – a specialist in the study of tissues.
Study Section 2: • Larynx – voice box; located at the upper part of the trachea. • Pharynx – throat; The pharynx is the common passageway for food and air entering the body. • Pituitary gland – Endocrine gland located at the base of the brain.
Study Section 2: • Thyroid gland – endocrine gland that surrounds the trachea in the neck. • Trachea – The windpipe – a tube leading from the throat to the bronchi. • Ureter – One of two tubes leading from each kidney to the urinary bladder.
Study Section 2: • Urethra – Tube from the urinary bladder to the outside of the body. • Uterus – The womb. The organ that holds the embryo and fetus as it develops. • Viscera – internal organs.
Body Cavities: • A body cavity is a space within the body that contains internal organs (viscera.) • Ventral cavities are found in the front of the body. • Dorsal cavities are found in the back.
Ventral Cavities: • Thoracic Cavity – Located in the upper half of the torso (thorax); the diaphragm separates the thoracic cavity from the abdominal cavity. • Abdominal Cavity – located in the middle portion of the torso (abdomen) • Pelvic Cavity – located within the pelvic girdle.
Dorsal Cavities: • Cranial Cavity – lies within the cranial vault; the hollow, enclosed portion of the skull. • Spinal Cavity – lies within the vertebrae. Also called the vertebral canal.
The Cranial Cavity: • Contains the brain and pituitary gland. • Is lined by the meninges surrounding the brain. • Regions of the cranial cavity (and the brain within) are named after adjacent bones (occipital, frontal, parietal, temporal, etc.)
The Thoracic Cavity: • Contains the heart, lungs, esophagus, trachea, bronchial tubes, thymus glad, aorta, and other large blood vessels. • Can be divided into two smaller cavities: • Pleural Cavity – space between the membranes that surround each lung. • Mediastinum – a centrally located area outside of and between the lungs. Contains the heart, aorta, trachea, esophagus, thymus gland, bronchi, and many lymph nodes.
The Abdominal Cavity: • Contains the stomach, small intestine, large intestines, spleen, pancreas, liver, and gallbladder. • Lined by a double folded membrane called the peritoneum. • Behind the peritoneum is the retroperitoneal space where the kidneys are located.
