Fetal Pig Dissection Lab

Biol 172 L November 01, 2016 Title: Fetal Pig Dissection Lab Purpose: In this lab, we dissected a fetal pig in order to better understand the location of body cavities. In addition, we explored what each cavity contained, and the functions thereof. By taking a look at this level, we further understood the ways in which the body systems interact to make function. We also gained better understanding about proper dissection procedures. Materials: Compound microscope Prepared slide of mammalian skin Preserved fetal pig dissecting pan Disposable gloves preservatives Plastic bag dissecting instruments Twine stereoscopic microscope Prepared slide of nervous tissue prepared slide of C.S. of spinal cord Exercise 22.1 Skin Histology Procedure: Observe a prepared slide of a mammalian skin (pig, monkey, or human) using a compound microscope. Result: Table 1: Tissues of the Skin and Their Functions Tissue Function Epidermis (Stratified Squamous Epithelium) Protection Dermis (Dense Connective Tissue) Provides strength and flexibility Stratum Corneum Provides natural physical and water-retaining barrier of the skin Stratum germinativum Gives rise to new cells for other epidermal layers Cuboidal Epithelium Protection -288925000 Figure 1: Skin Structure Discussion: How does the skin prevent dehydration? The skin acts as barrier that prevents the body from losing water it has already absorbed. If the internal and/or external body temperature rises, our sweat glands releases water that will evaporate and cool the body. How does the skin protect from bacterial invasion? It acts like an armor – the epithelial cells are tightly packed to create a barrier which prevents bacteria from getting in. It also provides an inhabitable environment for bacteria because of the salt, oil, low pH, skin removal, and swear make it hard for bacteria to live in Discuss how each of the ff. helps regulate body temp: blood vessels in the dermis, sweat glands, adipose tissue below the dermis, hair and hair follicles. The blood vessels regulate body temperature through vasoconstriction and vasodilation, sweat glands produces sweat that cools the skin using evaporation, adipose tissue below the dermis insulates the body temperature to keep the body warm, the hair allows additional insulation. when it is cold the arrector pili muscles makes an animal’s hair stand up, which warms him up, and the hair follicle secretes sweat that aids in evaporative cooling. Exercise 22.2 Meet your pig Procedure: Obtain a fetal pig and identify the body regions and all of the pig’s external structures. Which vessel – umbilical artery or umbilical vein – would carry blood high in oxygen? Umbilical vein Which vessel would carry blood low in oxygen? Umbilical artery Which vessel would carry blood high in nutrients? Umbilical vein Which vessel would carry blood high in metabolic waste? Umbilical artery Result: List structures observed in the fetal pig that are no longer present in the pig after birth. Umbilical vein, Umbilical cord, Allontoic stalk Discussion: The fetal pig demonstrated cephalization when it developed the mouth, eyes, ears, nose, as well as brain -17589522669500 Figure 2: Side View of Pig Exercise 22.3 Digestive system Procedure: Cut the corners of the mouth to expose the mouth cavity and identify the structures. Cut through the abdominal region of the pig, expose all the structures in the abdominal cavity and focus on the digestive system. Speculate about the contents of the space between the two epithelial membranes and its function. The parietal peritoneum and visceral peritoneum contains fluids for lubrication and for keeping the moistness. Speculate about the role played by these folds (gastric rugae). The folds are for the expansion of the stomach when full. Locate the cardiac valve and speculate about its function To prevent food from regurgitating back into the esophagus Speculate about the relationship between these vessels and food processing Transportation of nutrients from the intestine to the liver Imagine each band of muscle … do you know the special name given to the waves of contraction of these muscles? Peristalsis Result: The mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus. The liver and gallbladder Table 2: Divisions of the Body Cavity and Associated Membranes Body Cavity Divisions Epithelial Membrane Lining the Cavity Wall Epithelial Membrane Covering the Organs Organs Thoracic Pleural Parietal Pleura Visceral pleura Lungs Pericardial Parietal Pericardium Visceral pericardium Heart Abdominal Abdominal (peritoneal) Parietal peritoneum Visceral Peritoneum Stomach, pancreas, spleen, liver, gallbladder, intestines -17018011684000 Figure 3: Digestive Organs of the Abdominal Cavity Discussion: The colon or the large intestine absorbs more water to prevent dehydration. If the food passes too slowly, the colon absorbs too much water which may result to constipation, and if it passes too fast, the colon may not be able to absorb enough water and could lead to diarrhea. The digested food passes into the blood vessels in the wall of the small intestine through diffusion. The inner wall (mucosa) is covered in folds that project villi and microvilli. Villi and microvilli increases the surface area of the small intestine for the absorption of nutrients. The villi transport the nutrients to a network of capillaries and lacteals close to its surface. Exercise 23.1 Glands and respiratory structures of the neck and thoracic cavity Procedures: Open the thoracic cavity and study the major glands located in the neck region. -18097521336000 Result: Figure 4: Neck region and the thoracic cavity Exercise 23.2 The heart and the pulmonary blood circuit Procedure: Expose the pericardial cavity where the heart is located investigate its circulation and the pathway of blood to the lungs in the pulmonary circuit. What is the name of the epithelial lining adhering to the heart surface? Visceral pericardium Result: Right atrium – right tricuspid valve – right ventricle – pulmonary trunk – pulmonary arteries – pulmonary veins – left atrium Discussion: Arteries are blood vessels that deliver oxygen-rich blood from the heart to the tissues of the body, and veins are blood vessels that carries low-oxygenated blood from the body back to the heart. The pulmonary arteries are relatively small at the fetal stage of development because they are not being used. Having only one ventricle may result to the mixing of oxygen-rich blood and oxygen-poor blood. Exercise 23.3 The heart and the systemic circuit in the thorax Procedure: Identify the venae cava and their major branches and the branches of the aorta. Trace the dorsal aorta and note its small branches that carries blood to the ribs. Exercise 23.4 The systemic circuit in the abdominal cavity Lab Study A Procedure: Identify the branches of the dorsal aorta and the branches of the caudal vena cava. Lab Study B Procedure: Dissect the pancreas and review the flow of blood from the mesenteric arteries to the liver. Result: Aorta – cranial mesenteric artery – smaller mesenteric artery – capillary bed in the wall of the small intestine – mesenteric vein – lienogastric vein – hepatic portal vein – capillary bed (liver) – hepatic vein – caudal vena cava – heart Discussion: The liver’s function is to process nutrients from food, detoxify chemicals and metabolizes drugs in the body. When the digestive system begins to break down the food, the nutrients from it enters the blood and travels to the liver through the hepatic portal system. Then, the liver will start to process the nutrients in different ways. The liver also produces bile to help in the digestion of food. Drugs and toxins in the blood are removed when it passes the liver. Exercise 23.6 Fetal Pig Circulation Procedures: Observe the pig heart and identify the blood vessels and structures and trace the blood flow through the fetal pig. Would blood be high or low in oxygen in the caudal vena cava? High How would this hole change the flow of blood through the heart? The blood from the right atrium moves to the left atrium After leaving the left atrium, where would blood go next? Left ventricle Would blood in these branches be high or low in oxygen? Low Result: Ductus venosus, Caudal vena cava, Right atrium, Pulmonary trunk, Ductus arteriosis, Umbilical arteries, Foramen ovale, Left atrium, Ascending aorta. Discussion: More blood is allowed to flow into the placenta and bypass the lungs. Helps the blood to bypass the lungs. Exercise 23.7 Procedure: Study the respiratory system by locating the larynx, trachea, bronchi, bronchioles, alveoli and lobe of the lungs. Identify the epithelial lining of the pleural cavity. How would this epithelium be named? Simple squamous epithelium What is the name of the epithelial lining adhering to the lung surface? Visceral pleura Result: List, in order, the structures, tubes, and cellular barriers through which air passes as it travels from outside the body to the circulatory system of a pig, a terrestrial vertebrate. Mouth/sinuses – trachea – bronchi – bronchioles – alveoli – lobes of the lungs Discussion: In terrestrial vertebrates, what is the advantaged of having the surfaces for oxygen and carbon dioxide exchange embedded deep in lung tissue? It prevents water loss The capillaries that lie in close contact with the alveoli are branches of what blood vessel? The pulmonary artery The confluence of these capillaries forms what blood vessel? The pulmonary veins Compare blood composition in adult circulation with reference to oxygen and carbon dioxide between capillaries approaching alveoli and capillaries leaving alveoli. The capillaries approaching the alveoli contain low oxygen and high carbon dioxide, and the capillaries leaving the alveoli contain high oxygen and low carbon dioxide. 52070254000 Figure 5: Respiratory System Exercise 24.1 Excretory System Procedure: Locate the blood vessels serving kidney, then dissect the kidney to observe the renal cortex, renal medulla, renal pyramids, renal pelvis and the ureter Result: Describe the pathway of metabolic waste from the aorta to the outside of the body in the fetal pig. Aorta – renal artery – kidney – ureter – bladder – allantoic stalk – pig’s mom Discussion: How does the elimination of metabolic waste in the pig change after birth? After birth, the pig eliminates metabolic waste through urination and defecation. 018732500 Figure : C.S. of Kidney Exercise 24.2 Reproductive System: Be sure to draw reproductive structures for both sexes. Lab Study A: Male Pig Procedure: Expose the structures of the male reproductive system and observe them. Result and Discussion: Vasectomy is the most common form of human male sterilization used for birth control. Describe this process. The vas deferens is cut or tied preventing sperm to travel from the testes to the urethra. What structures identified are common to both the reproductive and excretory systems? Urethra and penis The testes develop inside the abdominal cavity and descend through the inguinal canal into the scrotum before birth. Explain the significance of the external scrotum and external testes in mammals. The external scrotum keeps the temperature of the scrotum ideal for the production of sperm. 018605500 Figure 6: Male Reproductive Lab Study A: Female Pig Procedures: Expose the female reproductive system and locate and observe the organs in this system. Result: Describe the pathway of an egg from the ovary to the outside of the body in a fetal pig, naming regions of organs when appropriate. Ovary – fallopian tube – uterus – cervix – vagina – vaginal vestibule – urethra -7302530035500 Figure 7: Female Reproductive System Exercise 24.3 Nervous tissue Lab Study A: Neurons Procedure: Observe a prepared slide of a nervous tissue using a compound microscope. 16573534480500Result: Figure 8: Prepared slide of a nerve tissue Lab Study B: Spinal Cord Procedure: Examine a prepared slide of a cross section of a spinal cord using a stereoscopic microscope. Result: Using the information from the study of the spinal cord, list in sequence the structures of neurons involved in the simplest reflex. Receptor Sensory neuron Integration center Motor neuron effector 018034000 Figure 9: C.S. of Spinal Cord Discussion: Most reflexes involve a specific sensor receptor, several sensory neurons, several interneurons, several motor neurons, and effectors. Propose a reflex arc that would result if you touched a hot plate in the lab. If you touched a hot plate in the lab, a response is created in the body. At the point of contact, skin receptors send nerve impulses to the spinal cord via sensory neurons, then to the interneurons. The impulses are then sent to motor neurons and stimulates the muscle (effector) to contract causing to snatch your hand away from the hot plate. Applying your Knowledge: The Peachtree Road Race is over, and you have just been awarded the coveted t-shirt. Your body is dripping wet and your skin appears bright red. Explain, from a physiological perspective, what is happening to your body. This is an example of how the body help maintain homeostasis. The nervous receptors senses stimuli and produces heat and the blood vessel dilate which allows more heat to escape. It also releases sweat so even more heat can escape. Tattooing is the risky and unregulated procedure of using a needle to deposit pigment in the skin. Where in the skin would it be necessary to deposit the pigment to make the tattoo permanent? To make the tattoo permanent, it should be deposited in the dermis with the use of a needle. The three most common form of skin cancer (1) basal cell carcinoma, (2) squamous cell carcinoma, and (3) malignant melanoma, the most dangerous skin cancer. Using your knowledge of skin histology, predict the skin layers and/or cells that are involved in each of these cancers. In basal cell carcinoma, the lowest layer of epidermis which is the basal cell layer is involved. The squamous cell carcinoma involves the abnormal version of squamous cell in the other layers of the skin. Lastly, malignant melanoma involves melanocytes which is the pigment-making cells of the skin. What differences would you expect to see in the appearance of lung tissue in adult and fetal pigs? Explain. The lungs of a fetal pig will appear dense and collapsed because it has not intake air while the lung tissue of an adult pig are more sponge like because it has been breathing air. The trachea is composed of rings of cartilage, whereas the nearby esophagus is composed of muscle and lacks cartilage. How are these structural differences related to the functions of each? The cartilage in the trachea allows respiration while the muscles of the esophagus allows food particles to pass through. More than any other organ in the body, the liver is most often damaged by excessive intake of substances such as alcohol, anabolic steroids, vitamin A, acetaminophen, and some prescription drugs, a condition called toxic hepatitis. Why would this be? When toxic blood passes through the liver, it takes away all the toxins from substances such as alcohol, anabolic steroid, etc. How would hypertrophy (swelling) of the prostate gland affect functioning of the excretory system? Hypertrophy of the prostate gland can make urinating difficult in men. It causes blockage by squeezing the urethra. Normally, a fatty encasements surround the kidney, helping to maintain its normal position in the body. In cases of extreme emaciation in humans – for example, as in anorexia – the kidney and propose one side effect to the kidney that could result from severe weight loss. Kidney stones may develop or even kidney failure A person who has lost a limb may experience phantom pain, the feeling of pain in the part of the body that is gone. Suggest an explanation for this phenomenon. The nerve endings in the part of the body that was amputated still send pain signals to the brain which makes the brain think that the body part is still there. Conclusion: In this lab, I was able to understand a basic idea of what cavities, systems, and organs looked like in a pig as well as having an introduction into dissection so that we could have a better understanding of the human body. We determined that our pig was a male and named him Wilbur. I now know how to use the different dissection tools, where or where not to cut during the procedure, as well as a good physical representation of what the insides of a body — in this case the pig’s cavities, systems, and organs — looks like.