LEANN FLETCHER Michael Fletcher was in the bathroom when he heard the gunshot. Fletcher ran out of the bathroom and found his wife, Leann, face down

Transcription

1 Body Systems

2 LEANN FLETCHER Michael Fletcher was in the bathroom when he heard the gunshot. Fletcher ran out of the bathroom and found his wife, Leann, face down in a pool of blood on their bedroom floor. Michael called 911 right away. When police and EMS arrived at the scene, Fletcher led them to the bedroom. A 45-caliber Smith and Wesson automatic pistol was lying next to Leann s right hand. During an initial assessment of the scene and the victim, it appeared that she suffered from a gunshot wound to the head. The cerebral artery is the primary source of oxygen-rich blood to the brain. Even after the artery had been severed, the heart had continued to pump blood to the brain for several seconds. Because of this blood flow, very dark, thick blood surrounded the victim. Upon arrival, emergency medical personnel determined that the victim showed no sign of life. The crime-scene unit arrived at the scene. After photographing the body, the medical examiner covered the victim s hands with bags to preserve trace evidence. Investigators collected and bagged the gun. The latent fingerprint expert dusted for fingerprints, and crime-scene investigators collected blood from the carpet.

3 Gravity caused the blood to pool in the parts of Leann s body that were touching the floor. Her thighs and face appeared bruised and bloated due to the pooling blood. Investigators estimated her time since death at just over an hour. Michael Fletcher was the only suspect in the case. Although he told the same story several times to several investigators, the investigators were unsettled by his statement. He said that he and his wife had just returned from the shooting range when he went into the bathroom. He had given the bullets to his wife to reload his gun. He said he heard the shot, ran out of the bathroom, and found his wife on the floor in a pool of blood. During the autopsy, the medical examiner performed a complete internal and external examination. Characteristics of the gunshot wound were consistent with being shot from 18 inches away. It would have been impossible for the victim to shoot herself from this distance. Michael Fletcher was arrested and charged with murder. A jury found him guilty of second degree murder. He was sentenced to life in prison. He is not eligible for parole until 2017.

4 INTRODUCTION The study of the structure of the human body is called anatomy. The study of the function of the body systems is physiology. Anatomy and physiology are often studied together because the structure of a cell or organ supports its function. Ex. The large surface area of a red blood cell (RBC) allows the cell to absorb and release oxygen and carbon dioxide (Anatomy). The shape also allows the cells to be flexible as they move through the blood vessels, preventing clotting (Anatomy). RBC carry oxygen to all the cells of the body and return carbon dioxide to the lungs (Physiology).

5 An understanding of anatomy and physiology is extremely important in forensic science. This knowledge allows scientists to interpret information about the crime from physical and biological evidence found at the crime scene. Your body systems work together to keep your body temperature, blood ph, and all other physical and chemical conditions relatively constant. This stable internal environment is called homeostasis.

6 THE CIRCULATORY SYSTEM Important in a death investigation. The major structuresheart, blood, arteries, and veins. The system is divided into two pathways systemic circulation and pulmonary circulation.

7 systemic circulation Uses the heart to pump oxygenated blood through the arteries to the entire body. The blood delivers oxygen and nutrients to cells. carries carbon dioxide and other cellular wastes away from cells. Veins carry the deoxygenated blood back to the heart.

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9 pulmonary circulation The heart pumps the deoxygenated blood, carbon dioxide, and other wastes to the lungs in pulmonary circulation In the lungs, the blood releases carbon dioxide and other wastes and picks up oxygen. The oxygenated blood then flows back to the heart to enter systemic circulation.

10 PROPERTIES OF BLOOD Blood is composed of red blood cells, white blood cells, platelets, and plasma. Figure 6-5 shows a red blood cell, a white blood cell, and a platelet.

11 Red Blood Cells Also called erythrocytes, carry oxygen throughout the body. The concave shape of red blood cells gives them a large surface area, which allows for efficient gas exchange. Hemoglobin is a protein in red blood cells. The hemoglobin binds to oxygen and transports it throughout the body.

12 Red Blood Cells (cont.) Red blood cells form in the bone marrow and live about 120 days. The production of red blood cells is controlled by the amount of oxygen in your body. If oxygen levels fall, the body produces more red blood cells. Oxygen levels fall when a person travels to higher elevations, where there is less oxygen. People who suffer from emphysema and other lung diseases may also have low oxygen levels. When oxygen levels return to normal, the body slows production of red blood cells.

13 White Blood Cells (WBC) Also called leukocytes. protect the body against infection and fight viruses and bacteria. A healthy person has between 5,000 and 10,000 WBC in each microliter of blood. The body produces more white blood cells when it encounters a virus or bacteria. doctors sometimes analyze WBC counts to check for infection. A white blood cell count of more than 10,500 may be an indication that the body is fighting an infection, such as tonsillitis or appendicitis. If the white blood cell count is below 3,500, the person s immune system is suppressed. Low WBC count can be caused by a variety of infections, including HIV, influenza, or malaria

14 Platelets Also called thrombocytes. Helps for blood clots when a blood vessel rips or tears. After the clot hardens, it becomes a scab. Patients with hemophilia have very low platelet counts. Without enough platelets, the body is not as able to form clots. Therefore, simple cuts can lead to severe bruising and internal bleeding. The loss of blood can cause death. Certain medications and medical conditions affect the body s normal blood-clotting mechanism.

15 Deep Vein Thrombosis Several other factors, including smoking, bed rest, and childbirth, increase a patient s risk of deepvein thrombosis (DVT). DVT is a condition in which a blood clot forms in a deep vein, such as a vein in a leg. If this clot is carried to the heart or lungs, it can cause heart attack, stroke, or a pulmonary embolism. DVT can be caused by Damage to a blood vessel wall or decreased blood flow as a result of physical trauma or surgery People who are not mobile after a surgery because their blood circulation has been affected. Certain prescription (heparin) and over-the-counter medications (aspirin), can reduce clotting.

16 Liquid portion of blood. 92% water & the rest is made up of salts, nutrients, enzymes, proteins, dissolved gases etc. responsible for transporting nutrients, vitamins, and gases & regulates ph, maintains fluid balance, and controls body temperature. Plasma

17 PATH OF BLOOD THROUGH THE HEART Human heart: divided into four chambers. upper chambers are called atria lower chambers are called ventricles. The right atrium receives the deoxygenated blood returning back to the heart. From the right atrium, it moves into the right ventricle through the tricuspid valve From the right ventricle, it is pumped into the pulmonary artery to the lungs.

18 The oxygenated blood returns to the left atrium via the pulmonary vein. From the left atrium, blood flows into the left ventricle through the bicuspid valve. From that it travels to the aorta and then to the rest of the body. Blood travels away from the heart toward the rest of the body through arteries. Blood flows back to the heart through veins. Pathway of Blood through the Heart

19 In the lungs: Capillaries the smallest blood vessels surround tiny air sacs in the lungs. The air sacs are called alveoli. Carbon dioxide diffuses from the blood in the capillaries into the alveoli. Oxygen diffuses from the alveoli into the blood in the capillaries-this process is called gas exchange.

20 FORENSIC IMPLICATIONS OF THE CIRCULATORY SYSTEM Blood found at a crime scene can be used to identify the victim or the perpetrator. Blood type is a class characteristic. Ex. if the victim had O blood, finding AB blood at the crime scene suggests that the perpetrator had that blood type. Many people may have that blood type, but suspects with any other blood type can be excluded. Nuclear DNA found in the blood can be used as individual evidence. Red blood cells do not have a nucleus or DNA. However, white blood cells have a nucleus and nuclear DNA. Except for identical twins, each person s nuclear DNA is unique. Therefore, DNA can be used to identify the victim or the perpetrator.

21 Blood is biological evidence it comes from a living or once-living source. When blood evidence is found at a crime scene, investigators ensure the integrity of the evidence through proper collection and evaluation techniques. when a red stain is found, investigators must ask three basic questions: Is it blood? Is it human blood? If it is human blood, can the blood be traced to a single person?

22 Hemastix (for spot stains) presumptive test used to indicate whether the red stain might be blood (Figure 6-8). plastic strips that have been treated with a special blood reagent. If the stain is blood, the reagent on the test strip turns green. (Iron in hemoglobin acts as a catalyst in this reaction) A catalyst is any substance that speeds up a chemical reaction.

23 Luminol (for large area of blood): presumptive test Mixed with hydrogen peroxide. During the reaction with hydrogen peroxide, the luminol is oxidized and light energy is released (see Figure 6-9). Therefore, the luminol test is viewed in a darkened area.

24 The leucomalachite green Presumptive test based on the same reaction in luminol but in the presence of iron: Leucomalachite green turns blue-green.

25 Kastle-Meyer test. Presumptive test A solution of phenolphthalein is used, which turns pink in the presence of traces of blood.

26 Collection of blood evidence: Bag each evidence in a paper bag separately to avoid crosscontamination of the evidence. If the blood evidence is found on a small object, such as a pencil or soda can, the object is packaged and the blood evidence is removed at the lab. If the blood evidence is found on a large object, such as a door or wall, only the blood evidence is collected. Investigators collect dried blood in a variety of ways. wet swab to remove the blood. place fingerprint tape over the blood and lift the stain, use a sharp instrument to scrape blood into a paper bag.

27 Note: Blood needs to be air dried. Drying the blood prevents mold or other microorganisms from forming. Microorganisms can destroy the evidence. Evidence collected from the suspect acts as a control or known sample.

28 When the heart stops pumping blood through the body, blood will travel in the direction of gravity, pools & changes the body changes color, especially in parts that are touching the ground. The pooling of blood in the direction of gravity is called lividity. Lividity Lividity begins to appear about 30 minutes to 2 hours after death and continues to become more apparent and darker for up to 12 hours.

29 The postmortem change in color caused by lividity is called livor mortis (see Figure 6-11). For the first few hours after death, livor mortis is not fixed. If the area of lividity is pressed, the pressure will push the pooled blood away from the spot. For a moment, the skin will lighten again. When the pressure is removed, the blood quickly pools again. After approximately 12 hours, however, the lividity becomes fixed irreversible and permanent.

30 Because lividity becomes fixed, forensic investigators can use it to determine whether the body was moved after the victim died. Within the first hours after death, patches of lividity in different areas of the body indicate the body has been moved. After lividity has become fixed, lividity that is not consistent with the position in which the body was found is an indication that the body was probably moved.

31 If an arm or leg is in a hanging position, such as over a bed or chair, when a person dies, petechiae may appear. Petechiae, small red dots underneath the surface of the skin, occur as capillaries near the skin rupture

32 Livor mortis a bluish-purple or reddish-purple color on parts of the body closest to the ground or floor. The color becomes darker as time passes because after death, oxygen begins to separate from hemoglobin. This change produces a purple pigment deoxyhemoglobin in the red blood cells. Areas away from the ground and at the edge of the lividity tend to be pink. However, variations in the color of the lividity can provide clues to the cause of death. Ex. victim of carbon monoxide poisoning is likely to show bright red lividity. Because cold temperatures slow the formation of deoxyhemoglobin, lividity in a victim of hypothermia will be bright pink. A body refrigerated shortly after death and the body of a victim of cyanide poisoning also exhibit bright pink lividity. Dark brown lividity indicates exposure to lethal doses of nitrates, aniline, and potassium chlorate. (herbicides)

33 Crime-scene investigators sometimes misinterpret lividity as bruising or signs of trauma. In such cases, an autopsy easily confirms the discolorations as livor mortis. Bruising is the result of blood leaking into extracellular spaces the spaces between cells. If the discoloration is indeed lividity, the blood will be confined to the blood vessels.

34 Blood Spatter Blood-spatter evidence is useful in helping investigators determine: the position of the victim at the time of the crime; the type of weapon or tool used; how many times the victim was hit, shot, or stabbed; whether the victim moved after the assault. After evaluating the blood spatter, investigators may be able to determine the following: What events transpired during the crime The sequence of events Who was or was not present

35 Experts use the laws of physics to interpret the blood spatter. Blood is viscous. Viscosity describes a liquid s resistance to flow Blood has high surface tension. Surface tension allows the blood spatter to retain much of its shape Blood Spatter

36 Blood Spatter Low-velocity splatter- caused by a stab wound, when the victim continues moving- the blood is likely to fall straight down, producing large droplets of blood on the ground. This blood spatter is said to be low-velocity spatter This type of spatter will likely form a pool of blood. Medium velocity blood spatter- caused by bluntforce trauma, ex. bat. This type of trauma causes blood to spurt out of the body.

37 A third pattern- arterial spray- based on the heartbeat pattern. Gunshot wounds produce high-velocity blood spatter. This type of spatter looks like tiny droplets, similar to a fine spray.

38 THE RESPIRATORY SYSTEM primary function bringing oxygen into the body & removing carbon dioxide and other gaseous wastes from it. The process of gas exchange is called respiration. The respiratory system interacts directly with the circulatory system. The respiratory system brings air into the lungs. The oxygen gas (O2) moves across the alveoli and capillary membranes into the bloodstream (the circulatory system). Carbon dioxide (CO2) moves into the lungs from the blood across the same membranes.

39 ORGANS OF THE RESPIRATORY SYSTEM The system is divided into two tracts the upper respiratory tract and the lower respiratory tract Look at the picture and know the organ in each tract

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41 The Nose The nose is made up of bone and cartilage. The two openings through which air can enter and exit are called nostrils. Tiny hairs inside the nostrils prevent large particles from entering the body. Some dangerous particles are able to enter the body through the nose even with the protection of the tiny hairs in the nose. Ex. anthrax People coat the bacterial spores with a powder to produce an airborne bio-weapon. Theses spores can get through the hairs in the nose and be inhaled into the lungs where the deadly bacteria are released. Behind the nose is a hollow area called the nasal cavity. The nasal septum divides the nasal cavity into two distinct sections.

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43 The pharynx (throat) bridge between the mouth and the esophagus. supports the production of sounds and speech.

44 The larynx (voicebox) large area slightly below the pharynx. composed of muscle and tissue. allows air to move into and out of the trachea and reduces the risk of toxic substances entering the lungs.

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46 Contains the vocal cords two pairs of horizontal vocal folds. The upper folds contain the false vocal cords which do not produce sound. muscles in the false vocal cords close the airway when a person swallows. The lower folds contain the true vocal cords. As air reaches these cords, the cords vibrate. The vibration generates sound waves. Contains the glottis & epiglottis which allow food and liquids to pass through the larynx without entering the trachea and air passages

47 long, narrow tube that travels from the larynx to the bronchi. Mucous coated cilia, or short, hair-like projections, line the walls of the trachea. The mucosa traps unwanted particles and moves them up and into the pharynx. Once in the pharynx, the unwanted material in the mucus can be swallowed. The trachea

48 Bronchi & Lungs Air moves from the trachea into two large tubes, called bronchi ( singular, bronchus). Each bronchus leads into a lung. The bronchi branch into two distinct parts the left bronchus and the right bronchus. These bronchi continue to branch into smaller and smaller tubes and structures inside the lungs. Capillaries line tiny air sacs, called alveoli, at the end of the bronchi. Gas exchange takes place between the alveoli and the capillaries. Oxygen diffuses across cell membranes from the alveoli into the blood in the capillaries. Carbon dioxide diffuses from the blood into the alveoli. The right lung is divided into three lobes and is larger than the left lung. The left lung is divided into only two lobes.

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50 FORENSIC IMPLICATIONS OF THE RESPIRATORY SYSTEM The process of using oxygen and producing carbon dioxide on a cellular level is called cellular respiration. Cellular respiration involves many individual reactions. summarized by the following equation:

51 Without oxygen, a person will eventually die. Ex. in a fire, a person may die of asphyxiation, a condition in which the amount of available oxygen decreases sharply while the level of toxic gases (especially carbon monoxide) increases. Suffocation can occur when the amount of available oxygen is stopped or slowed quickly. Sealing a plastic bag over a person s head blocks available oxygen. The person will soon pass out & die

52 If a person is found in water, a medical examiner might be able to determine whether the victim drowned or was placed in the water after death. If the medical examiner finds water in the lungs that is consistent with the water where the victim was found, the victim likely drowned. If, however, the medical examiner determines that there is no water in the lungs, the victim might not have drowned. Instead, the body might have been placed in the water after death.

53 THE MUSCULAR SYSTEM Muscles provide the most basic conscious and unconscious movements. Voluntary movements are movements you intend to make and include walking, waving, and many facial movements. Involuntary movements are movements, such as breathing and digestion, which you do not control completely.

54 TYPES OF MUSCLES three types of muscle skeletal, smooth, and cardiac. Skeletal muscle-responsible for voluntary movement and is attached to bone. Two kinds of protein actin and myosin form fibers within muscles called myofibrils. The organization of the myofibrils in skeletal muscles produces light and dark bands, or striations. The myosin and actin work together to allow a muscle to contract and relax.

55 Smooth muscle-found in internal organs, such as the stomach or bladder. Smooth muscles have no striations and are not under voluntary control. Cardiac muscle-found only in the heart. It is striated and very complex. It is not under voluntary control.

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57 FORENSIC IMPORTANCE OF THE MUSCULAR SYSTEM Because oxygen is no longer present after death, no additional ATP is produced in the cells. Actin and myosin are no longer able to relax to extend the skeletal muscles, and the muscles become stiff. The process in which the muscles of a body begin to stiffen is called rigor mortis.

58 rigor mortis. begins about two hours after someone dies. The small muscles in the face are the first to become stiff, and rigor eventually spreads throughout the entire body in about 12 hours. Rigor can last from 24 to 48 hours. After rigor mortis, the body tissues begin to decay, digestive enzymes leak from the lysosomes in the cells and the muscles relax. The length of time rigor lasts depends on the condition of the body at death and on atmospheric conditions, such as temperature and humidity.

59 THE FORENSIC IMPLICATIONS OF OTHER BODY SYSTEMS

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