Three Watson Irvine, CA 92618-2767 Website: www.sdlback.com HUMAN BODY HUMAN BODY TITLES IN THIS SERIES Animal World Earth Human Body Machines & Inventions Plants Universe HUMAN BODY SADDLEBACK’S Human Body Copyright © 2008 by Saddleback Educational Publishing All rights reserved. No part of this book may be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system without the written permission of the publisher. ISBN-10: 1-59905-234-2 ISBN-13: 978-1-59905-234-2 eBook: 978-1-60291-596-1 2 Weight of Brain The brain weighs less than 2.5% of our total body weight, but it burns oxygen and glucose at ten times the rate of other body organs. • Healthy people can live with only one kidney. • There are three types of blood vessels: arteries, veins, and capillaries. • Blood vessels provide two important means of measuring vital health statistics: pulse and blood pressure. • The tooth is the only part of the human body that cannot repair itself. • For humans, the normal pulse is 70 heartbeats per minute. • It takes more muscles to frown than it does to smile. • The brain is more active and thinks more at night than during the day. • The human brain is 80% water. • Your fingernails grow almost four times as fast as your toenails. Length of Intestine The small intestine in human beings is 19.68 feet long. Human Body T he human body is an organized collection of several body systems, which perform specialized functions. Some of these body systems, such as nervous, skeletal, and muscular are found throughout the body, while some systems, such as digestive, urinary, and endocrine are located in smaller areas. 3 T he human body is made up of billions of cells. Cells are the basic structural and functional units of the human body. Tissues are an organization of several similar cells along with various intercellular substances between them. Organs are an organization of several different kinds of tissues arranged together to perform special functions. Largest Organ Skin is the largest organ of the human body. Dissimilar Person Similar DNA Any two unrelated strangers anywhere on the planet share 99.9 percent of the same DNA. Cells, Tissues, and Organs • Intercellular matrix is a non-living material, which fills the space between the cells. • Epithelial cells may be squamous, cuboidal, or columnar in shape and may be arranged in single or multiple layers. • Nerve cells or neurons are cells in nervous tissue that generate and conduct impulses. • There are about 210 different types of cells in the human body. • Human cells are made of several smaller organelles, such as nucleus, endoplasmic reticulum, golgi complex, lysosomes, and mitochondria. • There are four types of tissues in the human body: epithelium, connective, muscles, and nervous tissues. • Epithelium tissues cover organ surfaces and serve as protection and absorption. 4 B ody systems are the most complex components of the human body. They are an organization of several organs that perform complex functions for the body. The major body systems include circulatory, digestive, endocrine, immune, lymphatic, muscular, nervous, reproductive, respiratory, skeletal, and urinary. Combined Body Systems The functions of many body systems often overlap. For instance, the muscular and skeletal systems function together. As a result, both are sometimes combined and studied under the musculoskeletal system. • The muscular system allows the human body to move. • The circulatory system moves substances to and from the body cells. • The lymphatic system or immune system defends the body against diseases. • The skeletal system supports the human body and protects its internal organs. • The nervous system carries messages from the body to the brain and from the brain to the body. • The digestive system digests food and extracts energy and nutrients from it. • The respiratory system controls the gaseous exchange in the human body. • The endocrine system controls the secretion of hormones. Body Systems 5 • The skeleton is the internal structure that holds the human body up and with the help of the muscular system, allows us to move. • Bones are the most important part of the skeletal system. • The longest bone of the skeletal system is the thighbone or femur. • The stirrup bone inside the ear is the smallest bone of the skeletal system. • Muscles hold the bones together and allow them to move. T he skeletal system provides support to the human body. It also protects delicate internal organs. The skeletal system is made of individual or joined bones. These bones are supported by ligaments, tendons, muscles, and cartilage. The skeleton continues to change its composition over a lifespan. On average, an adult human has 206 bones, but a baby is born with approximately 270 bones. Types of Skeleton There are two types of skeleton in the human body: the axial skeleton and the appendicular skeleton. Blood Forming Tissue The skeleton contains bone marrow, the blood forming tissue. Skeletal System 6 B ones are hard endoskeletal connective tissues. They support body structures and protect internal organs. There are two types of bone tissues: compact and spongy. They differ in density. Most bones contain both types of tissues. Types of Bones There are four categories of bones: long, short, flat, and irregular bones. Producer and Store Bones manufacture blood cells and store for useful minerals. • The bone that is broken most often is the collarbone. The scientific name for the collarbone is the clavicle . • The hyoid bone in the throat is the only bone in the body that is not attached to any other bone. • The human hand has 27 bones; your face has 14! • There are over 230 movable and semi-movable joints in the body. • Bones in men tend to be larger and heavier than in women. • The place where two bones meet is called a joint. Some joints move and others don’t. Bones are Active Bone cells rely on blood to keep them alive. Bone 7 • The lower part of the upper jaw holds the upper teeth. • Baby teeth start appearing at the age of 6 or 7 months. • The real name for baby teeth is milk teeth. • The hardest thing in the body is the enamel. • The first permanent teeth appear at about the age of six. • Human adults have 32 teeth called permanent teeth. • Human beings have three kinds of teeth: incisors, canines, and molars. • A tooth is fixed into the bony jaw socket and held in place by cement. • Digestion starts in mouth with teeth. T eeth are hard structures attached to the jaws. They are used for grinding and chewing food. The jaw is made up of two opposed bony structures that form the entrance of the mouth. The jaw consists of the upper and lower jaw. The upper jaw is known as the maxilla and the lower jaw is known as the mandible. The upper jaw is fixed while the lower jaw can move. Working Mechanism of Jaws The movement in the jaw is brought with the help of several muscles that are known as muscles of mastication. Permanent Teeth An adult has 32 permanent teeth that start to grow at about the age of 5–6 years. Teeth and Jaw 8 L igaments are also found in many organs, such as the uterus, bladder, liver, and diaphragm. Ligaments are fibrous bands that are made of collagen. They keep the joints stable and allow flexibility and movement. Tendons are the fibrous connective tissues. They connect muscles to bones. Ligament System in Spine There are two primary ligament systems in the spine: intrasegmental and intersegmental systems. • Bones are connected to each other by ligaments. • The muscles are attached to the bones with the help of tendons. • Ligaments and tendons may take a long time to heal after an injury because their blood supply is limited. • Tendons carry tensile forces from muscles to bones. • The word “ligament” comes from the Latin word ligamentum , meaning a band or tie. • If a ligament is made up of several thick bands of fibrous branches, it is called a “collateral ligament.” Ligaments and Tendons Desmology “Desmology” is the study of ligaments. 9 [...]... the human body after bone marrow Muscular System T he muscular system is the network of muscles found in the human body The system facilitates and allows movement of the body The muscular system is also responsible for the functioning of important organs in the body such as heart and lungs It also helps in keeping the body warm Busiest Muscle in the Body Eye muscles are the busiest muscle in the body. .. average human has about 1.47 gallons of blood in the body 22 • Except the heart and lungs, all the other parts of the body receive their blood supply from the aorta • The aorta is the largest artery of the body • The pulmonary vein is the only vein in the human body that carries oxygenated blood, while all the other veins in the body carry de-oxygenated blood • The red blood cells circle the whole body. .. largest muscle in the body is the gluteus maximus found in the buttocks • There are 630 active muscles in your body and they act in groups • Massete muscles are the strongest muscles of the body found on each side of jaw • A smile uses 17 muscles while a frown uses 43 11 Muscles in Our Body T here are more than 600 muscles in the human body These muscles are found all over the body Muscles that are... covering of the human body On average, the skin covers about 2 square yards of surface area The primary job of the skin is to protect the body from external dangers It also defends the body against infections and acts as a sensory organ detecting temperature, touch, and vibration Body Temperature Control By distributing heat through the skin and by preventing dehydration, skin helps to control body temperature... through receptors in the skin • The adult human brain is about 2% of the total body weight • One human brain generates more electrical impulses in a single day than all of the world’s telephones put together 15 Spinal Cord T he spinal cord is a part of the central nervous system It is a bundle of nerves that carries messages between the brain and the other parts of the body The spinal cord is protected by... When the body is infected, it increases the production of white blood cells This leads to the enlargement of lymph nodes Distribution The human body has about 500 to 600 lymph nodes They are mostly found in the underarms, groin, neck, chest, and abdomen Antigens and Antibodies A ntigens are molecules, often found on foreign substances such as bacteria or viruses They cause diseases in the body The... information system of the body It collects, stores, and analyzes all the information received by the body The nervous system is the control system of the body It is divided into two parts – the central nervous system and the peripheral nervous system The entire nervous system is made of nervous tissues Nerve Impulses A nerve cell can transmit 1,000 nerve impulses each second • The human nervous system consists... and nutrients to the body s tissues and removes waste from them Blood consists of plasma—a watery liquid— and three specialized cells The specialized cells of the blood are: red blood cells, white blood cells, and platelets Red blood cells carry oxygen throughout the body, white blood cells protect the body from diseases, and platelets help in the clotting of the blood Blood Groups Human blood is grouped... severed Size of Eyes Eyes remain the same size throughout life • The eye is the only part of the human body that can function at 100% ability at any moment, day or night, without rest • The human eyeball measures only about 98 inches • The Ishihara test is a test used to detect your ability to see colors • The human eye blinks an average of 4,200,000 times a year • The retina is responsible for converting... specialized receptor cells of the olfactory epithelium These are called olfactory receptor neurons • The average human being is able to recognize approximately 10,000 different odors • A diminished sense of taste is known as hypogeusia • Flavor is what people commonly call the “taste” of food • There are five basic tastes: salt, sour, sweet, bitter, and umami • Humans have seven primary odors that . 92618-2767 Website: www.sdlback.com HUMAN BODY HUMAN BODY TITLES IN THIS SERIES Animal World Earth Human Body Machines & Inventions Plants Universe HUMAN BODY SADDLEBACK’S Human Body Copyright © 2008. The human brain is 80% water. • Your fingernails grow almost four times as fast as your toenails. Length of Intestine The small intestine in human beings is 19.68 feet long. Human Body T he human. gaseous exchange in the human body. • The endocrine system controls the secretion of hormones. Body Systems 5 • The skeleton is the internal structure that holds the human body up and with the