HUMAN BODY SYSTEMS 1 IIIIINNNNNTTTTTRRRRROOOOODDDDDUUUUUCCCCCTTTTTIIIIIOOOOONNNNN Who are we? We can learn the answer to this question by observing, hypothesizing, experimenting, and analysing. We are complex living beings in a complex, contradictory, ever-changing world. We know that we do not understand everything about ourselves, but by using this scientific method we can keep learning more and more. Without our bodies we are nothing. A person cannot exist without a body. In this book you can see pictures of some basic structures of the human body. You can also begin to see the interconnections between the different parts of the body in order to understand how the body functions. We should warn you that there are two serious misconceptions that you may get from this book. One misconception is that any part of the human body exists in a static state. Actually everything in the body is in a constant state of movement and change. It is constantly being broken down and rebuilt. Every thing is in the process of becoming something else. Actually, we are not made of things, but of processes. Thus, on the left-hand pages, we have briefly discussed some of the processes and functions of the structures seen on the right-hand pages. The second misconception is that the human body systems exist as separate entities. They cannot function separately. They are all interconnected and dependent on each other. Some of the same organs even belong to more than one system. For example, the long bones appear in both the skeletal and the lymphatic systems, since in addition to providing support they also manufacture blood cells. The ovaries appear in both the hormonal and the reproductive systems, since they produce both hormones and ova. These human body systems are merely useful ways of classifying and studying the structure and function of the body. All together they function and interact with each other and with the surroundings to produce a conscious, living human being. 2 CCCCCOOOOONNNNNTTTTTEEEEENNNNNTTTTTSSSSS Skeletal system ....................................... 4 Muscular system ..................................... 6 Digestive system ..................................... 8 Respiratory system................................ 10 Circulatory system................................. 12 Lymphatic system ................................. 14 Nervous system..................................... 16 Endocrine system ................................. 18 Urinary system ...................................... 20 Reproductive system............................. 22 How to use this book............................. 24 Index...................................................... 26 3 1 SSSSSKKKKKEEEEELLLLLEEEEETTTTTAAAAALLLLL SSSSSYYYYYSSSSSTTTTTEEEEEMMMMM OOOOOUUUUURRRRR Our skeleton consists of all our bones, teeth, cartilage, and joints. Some bones protect our internal organs. Some bones provide a framework for the body (just as the spokes of an umbrella provide a framework). Some bones contain red marrow that produces blood cells and yellow marrow that also stores fat. Cranium Yellow marrow Red marrow The Skull: Cartilage the bones that enclose the brain and support the Cartilage is softer than bones and is face and teeth somewhat flexible, like rubber. Maxilla Mandible (jaw bone) Cartilage (shown here in white) connects the ribs to the sternum, The Backbone allowing the ribs to move as we (the spinal column) breathe. The backbone is made of vertebrae (side view) Cartilage supports our nose and outer ears. Disc Joints contain some cartillage. Spinal cord birth 4 years One vertebra (top view) 13 years A rib attaches here adult Much of an infant’s skeleton consists of The spinal cord Tailbone cartillage, which is gradually replaced by bone. passes through (coccyx) this hole 4 Skull Spinal column (backbone) Clavicle (collar bone) Scapula (shoulder blade) Sternum (breast bone) Ribs Humerus Radius Ulna Pelvis Tailbone (coccyx) Carpals Metacarpals Phallanges Femur Patella Fibula Tibia Tarsals Metatarsals Phallanges Calcaneus 5 22222 MMMMMUUUUUSSSSSCCCCCUUUUULLLLLAAAAARRRRR SSSSSYYYYYSSSSSTTTTTEEEEEMMMMM OOOOOUUUUURRRRR There are three kinds of muscles: 1 How do muscles Skeletal muscle make us move? These muscles are attached to bones. They are also called ‘voluntary Tendons attach one end of the biceps muscles’ because we can and triceps to the shoulder blade and the other end to the radius or ulna. Each consciously contract them. muscle can pull, but it cannot push. That (shown at right and on the is why two muscles are needed to bend facing page) the arm back and forth at the elbow. The biceps contracts, 2 pulling the radius in, Smooth muscle while the triceps relaxes These are found in the walls the stomach shoulder muscles of the digestive tract, urinary blade bladder, arteries, and other tendon internal organs. They are ‘involuntary muscles’ because we do not consciously control them. biceps 3 triceps Cardiac muscle humerus These are the muscles radius of the heart.Their contraction radius ulna is involuntary and continues pivot point in a coordinated rhythm as long as we live. The triceps contracts, pulling the ulna Some muscles of the back to the extended Occipatalis Latissimus dorsi position, while pulls the rotates and head back extends the arm, the biceps draws shoulder relaxes. Trapezius down and back Ligaments attaching the wrist bones to each other. Tendons attach muscles to bones. Ligaments attach bones to bones. Gluteus maximus rotates and extends 6 the thigh Frontalis raises the eyebrows Occuli Orbicularis closes the eyelids Orbicularis oris closes the lips Trapezius raises, rotates, or draws back the shoulders, and pulls the head back or to the side Deltoid raises and rotates the arm Pectorals draw the shoulder forward and rotates the arm inward Biceps bends the arm at the elbow Triceps straightens the elbow Rectus abdominus draws the abdomen in Finger flexors bend the fingers Finger extensors (behind) straighten the fingers Sartorius bends the hip or knee and rotates the thigh outward Adductor rotates the leg sideways Quadriceps femoris straightens the knee or bends the hip joint Gastrocnemius bends the knee and lifts the heel Soleus extends the foot forward Peroneus extends the foot and turns it outward 7 33333 DDDDDIIIIIGGGGGEEEEESSSSSTTTTTIIIIIVVVVVEEEEE SSSSSYYYYYSSSSSTTTTTEEEEEMMMMM SMALL INTESTINE OOOOOUUUUURRRRR Every cell in our body does work. Work requires energy, which is supplied by the food we eat. Food also supplies the small moNleecwu lTeesx thtat are the building blocks for cell maintainance, growth, and function. Digestion breaks down food into materials the body can use: 1. Your sense receptors 3. Your stomach stores food so work together with your that you need not eat con- Artery brain to make you tinously. It also breaks down hungry. Saliva increases food with acid and enzymes. Vein (you produce more than 1 litre/day), and helps 4. The salivary glands, digest food while it is pancreas, liver, and mechanically torn, cut, gallbladder secrete and crushed, and ground in store digestive juices. your mouth. 5. The small intestine is where 2. The passages of your most of the chemical digestion dwigitehs itnivveo sluynstteamry amreu lsicnleeds abnlodo ndusttrreieanmt atabkseosr pptliaocne .into the Finotledsst iinna lthe that contract in waves to Muscles lining squeeze food along. 6. The large intestine reclaims water and releases waste. The Intestinal Wall In order to increase its surface area, the SWALLOWING intestinal wall is folded, and each fold is lined When swallowing, muscles move the epiglotis down to close the opening with villi. This way, more cells come into contact to the trachea, so that food and drink do not enter the lungs. The soft with nutrients in the digested food. Nutrients palate also moves up, so that food does not go up the nasal passage. enter the epethelial cells that line the villi, either epiglottis up epiglottis down by diffusion or active transport. They are then to breathe to swallow food absorbed by capillaries and lymph vessels. Capillaries transport the nutrients to larger blood vessels, then to the portal vein,which Soft goes to the liver. Then the nutrients go to the palate heart, to be pumped to the rest of the body. Tongue Epiglottis Food Villi Oesaphagus Trachea Epithelial cells The stomach does not have Artery one fixed shape Vein Everyone’s internal organs are slightly different. The shape and position of your stomach also depends on how much food it contains, and whether you are Capillary standing or lying down. Lymph vessel 0.5 mm 8 Mouth starts mechanical and chemical digestion of food with the help of teeth, tongue, and saliva Salivary glands produces saliva, which helps lubricate food for easier swallowing; contains antibacterial agents and the enzyme amylase, which breaks down starch Pharynx entering food triggers its swallowing reflex Oesophagus a muscular tube that squeezes food along to the stomach Stomach stores, mixes, and digests food with the gastric juice it produces, which consists of mucus, enzymes, and hydrochloric acid, producing acid chyme Liver blood carrying nutrients from the small intestine passes through the liver, which filters it and breaks down and synthesizes proteins, breaks Waist down carbohydrates into glucose and glycogen, produces bile Gallbladder collects bile from the liver, and discharges it into the small intestines, where it helps digest fat Pancreas a gland that produces digestive enzymes and an alkaline solution that neutralizes the acid chyme that comes from the stomach; it also secretes the hormone, insulin Small intestine a 6 metre long tube in which most of chemical digestion occurs; nutrients are absorbed from here into the bloodstream Large intestine absorbs water from the food wastes that have not been digested in the small intestine; also absorbs some important vitamins that are produced by the large numbers of bacteria it harbours Rectum stores feces (which consist mainly of indigestible plant fibres, bacteria, and water) until they can be eliminated from the body through the anus 9 44444 RRRRREEEEESSSSSPPPPPIIIIIRRRRRAAAAATTTTTOOOOORRRRRYYYYY SSSSSYYYYYSSSSSTTTTTEEEEEMMMMM OOOOOUUUUURRRRR THE LUNGS Through respiration we exchange gases with our environment. Our cells require a continuous Trachea supply of oxygen (O ) in order to obtain energy 2 from food molecules. Cells would also die if they were not able to get rid of the carbon dioxide (CO ) they produce. 2 The 3 Processes of Gas Exchange: 1. In our lungs, O passes from the air into our 2 blood, and CO passes from our blood into the 2 air. Some water vapour is also released into the air. 2. Our circulatory system transports O and CO 2 2 to and from all the parts of our body. Haemoglobin molecules in our red blood cells transport O . 2 3. Cells take up O and release CO 2 2 Bronchus Mucus membranes line air passages Bronchiole Cilia move in waves Mucus Dirt to clear out mucus gland Mucus The lungs are sacs made of pleural containing dirt particles. membranes, containing a dense lattice of tubes: bronchi, and the smaller bronchioles. When we inhale air, it travels through this network and fills the tiny air sacs called alveoli. That is where gas Alveoli Bronchiole exchange with the blood in capillaries takes place. Alveoli Close-up Hairs in our nostrils, as well as mucus and cilia Alveoli throughout our air passages When we help remove dirt that enters Capillaries the respiratory system in the inhale, air we breathe. Most of the where does mucus and dirt is swallowed Air the air go? and passes into the oesophagus and out through Nostrils the digestive system. i Nasal cavity i What happens in the aveoli? Pharynx O from the air diffuses through the thin layer i 2 of cells that forms the aveoli walls. Then it enters the web of capillaries that surround Larynx i each aveoli. CO goes in the opposite 2 direction, from the capillaries to the air. Trachia i In the capillaries, O diffuses into red blood 2 cells. Red blood cells contain protein Bronchus molecules called haemoglobin, which i contain iron atoms. Each iron atom can carry an O molecule. When haemoglobin binds Bronchiole 2 i O it turns red. Blood without oxygen looks 2 bluish - after passing through the lungs it Alveolus turns red. 10