أحتاج لمساعدة عاجلة
الأستاذة الله يعطيها العافية لقت المادة قليلة علينا وعنا كم يوم إجازة قررت إضافة موضوع علينا وبصراحة أنا تصعبت منو
ونفسي حدا يشرح لي إياة
RESPIRATORY SYSTEM
Objectives
1. Identify and describe the function of the main organs and structures in the respiratory system.
2. Describe the movement of air into and out of the lungs.
3. Apply this knowledge to organismal adaptive strategies and problems in human physiology.
The respiratory system is responsible for bringing a fresh supply of oxygen to the blood stream and carrying off excess carbon dioxide. In mammals, air enters the body through the external nares and enters the nasal cavities dorsal to the hard palate. As air passes through these convoluted cavities, it is humidified and warmed to body temperature and dust is caught in the mucus of the membranes that line the cavities. Air moves from here into the nasopharynx, where it passes through the glottis into the larynx. Carefully cut the soft palate longitudinally to examine the nasopharynx of your specimen.
The larynx is a hard-walled chamber composed of cartilaginous tissue. In the course of hominid evolution, the larynx has moved downward (caudally). As a result, human vocalizations tend to come out of the mouth, where the tongue can manipulate them. In chimps, the larynx is higher in the throat, with the result that vocalizations are very nasal (and thus less controllable and understandable). Our descended larynx comes with a price – it makes choking on food far more likely. Interestingly, human babies retain an elevated larynx. It makes baby talk difficult, but it also allows babies to nurse and breathe at the same time.
Slit the larynx longitudinally to expose the vocal cords. The vocal cords are elastic ridges that stretch across the space within the larynx. When air passes over the vocal cords during exhalation, the cords vibrate and produce sound. In adult humans, laryngitis results from viral infection of the vocal cords. They swell and regular speech is difficult to impossible.
Read the following information about the respiratory system. However, do not attempt to identify structures other than the trachea until you have exposed the heart and its major vessels (see Circulatory System further below).
The trachea, distinguished by its cartilaginous rings (incomplete on the dorsal side), divides into the two bronchi (singular bronchus), which enter the lungs and divide into bronchioles (don’t try to find the bronchi until you’ve finished examining the heart and its major vessels). Bronchioles terminate in alveoli, where gas exchange takes place.
The right lung typically consists of four lobes and the left of two or three. How many does your pig have? The lungs in your fetal pig are small and fairly solid because they have never been inflated. Inflation causes lungs to have a spongy appearance. Note the position of the diaphragm in relation to the lungs. Contraction of the diaphragm enlarges the thoracic cavity and pulls air into the lungs. Remember that only mammals have a true muscular diaphragm; other terrestrial vertebrates use a variety of methods to inflate their lungs.
Examine the lungs and note the pleural membranes (one lining the inner surface of the pleural cavity and the other covering the outer surface of the lung). As mentioned earlier, the intrapleural space is filled with fluid. This fluid allows the membranes to slide freely across each other, much like two wet panes of glass (easy to slide, hard to separate), and allows them to maintain contact. This ensures that the lungs will inflate when the thoracic cavity expands as a result of diaphragmatic contraction or expansion of the rib cage.
When neonatal mammals inhale for the first time, their lungs inflate. When they then exhale, the lungs don’t deflate all the way. That’s because pulmonary surfactants reduce the surface tension of water (just like soap does – you can float a bottlecap on water until you add a surfactant like soap). In this case the water is in the form of a film that coats each and every alveolus. If it weren’t for these surfactants, the surface tension of this layer would collapse the delicate alveoli – causing the lungs to “collapse” after each breath. This surfactant is produced by the lungs during the last part of pregnancy.
Think about it
1. Why does the trachea have cartilaginous rings?
2. Why is it important for air to be moist when it enters the lungs? Many desert mammals have extremely convoluted nasal cavities. How might these large and complex nasal cavities conserve water during exhalation?
3. When you catch a cold, you get a runny nose. Is snot your body’s way of combating a viral invader, or is the virus simply using you to reproduce and spread itself? The common cold generally doesn't land you in bed: is this evidence of you're own abilities to "fight" the virus, or is the virus manipulating you to maximize its exposure to uninfected individuals?
4. What is the function of the eustachian tubes?
CIRCULATORY SYSTEM
Objectives
1. Identify and describe the function of the main organs and structures in the circulatory system.
2. Trace the flow of blood through the pulmonary and systemic circuits.
3. Describe how the circulatory and respiratory systems work together to bring about the integrated functioning of the body.
4. Understand portal circulation.
5. Understand mammalian fetal circulation from a mechanical, physiological, and evolutionary perspective.
The circulatory (or cardiovascular) system is responsible for transporting nutrients, gases, hormones, and metabolic wastes to and from individual cells. Actually, the loading and unloading take place in capillaries. Oxygen is added to the blood (and carbon dioxide removed) in the capillaries of the lungs. In the capillaries of the small intestine, nutrients are added to the blood, while in the capillaries of the kidneys the blood is cleansed of various metabolic wastes and excess ions.
In mammals, the circulatory system is divided into a pulmonary circuit, which involves blood flow to and from the lungs, and the systemic circuit, which involves blood flow to and from the rest of the body. Your pig has been doubly injected (red for arteries, blue for veins). However, note that in reality, arteries and veins are defined by the direction of blood flow, not by the oxygen content of the blood contained therein.
1. The Heart (Fig. 6)
You may remove as much thymus as you need to in order to view the heart. Carefully remove the pericardial sac from the heart. In living animals, the pericardial cavity is filled with fluid that acts as a shock absorber to protect the heart from injury. Identify the coronary artery and coronary vein lying in the diagonal groove between the 2 ventricles. These vessels supply and drain the heart (the heart is a muscle and as such has the same requirements of any other organ). When the coronary artery becomes obstructed, a heart attack may occur. It is the coronary arteries that are "bypassed" in coronary bypass surgery. Note that the atria have external flaps, known as auricles.
In an adult mammal (fetal circulation will be discussed below), deoxygenated blood flows into the right atrium from the anterior and posterior vena cavae. It then makes the following circuit: right ventricle, pulmonary trunk, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aortic arch, aorta, and on into the systemic circulation. On the heart model, trace this path and find the above as well as the following structures:
• right atrioventricular valve
• atrioventricular valve
• right semilunar valve (between right ventricle and pulmonary trunk)
• left semilunar valve (between left ventricle and aorta)
• papillary muscles: support chordae tendinae
• chordae tendinae: support AV valves, preventing eversion
2. Major veins of the systemic circulation, anterior to the heart (Fig. 7a)
Following the path of deoxygenated blood, find the external jugular vein, which drains the head and neck, and the internal jugular vein, which drains the brain. Note the vagus nerve running between the right common carotid artery and the internal jugular vein (the vagus nerve is responsible for slowing the heart, constricting bronchi, and stimulating the stomach and gallbladder). The jugular veins meet with the subclavian vein to form the brachiocephalic vein. The right and left brachiocephalic veins join to form the anterior (cranial) vena cava. Note, however, that the mass of veins (and arteries) anterior to the heart may not look exactly like what you see in the figure. For example, do the external and internal jugulars join before reaching the brachiocephalic? Does your pig even have a subclavian vein? or do the subscapular (from the shoulder) and axillary (from the arm) veins empty straight into the brachiocephalic vein? How substantial is the brachiocephalic vein? or do the subclavian and jugulars empty straight into the vena cava? Make sure you examine other pigs to appreciate the variability of these vessels.
Fig. 6. The heart and major arteries and veins.
3. Major arteries of the systemic circulation, anterior to the heart (Fig. 7b)
Viewing the major thoracic arteries may require moving (but not removing) some of the thoracic veins (attempt the former before resorting to the latter since you will see them on the lab practical). Like the veins, however, there is a great deal of variation in the branching patterns of the brachiocephalic trunk and the left subclavian artery. The first large vessel that branches from the aortic arch is the brachiocephalic trunk. This artery soon branches into the right subclavian and the common carotid arteries (as well as sending vessels along the inner and outer walls of the rib cage). The subclavian arteries carry blood to the forelimbs, the carotid arteries carry blood to the head. The carotid branches into an internal carotid, which goes to the brain, and the external carotid, which goes to the face. In desert-dwelling ungulates, the internal carotid forms an arterial "capillary" bed (rete) over the nasal passages and then reforms the carotid artery and delivers blood to the brain. Because the nasal passages represent the intersection of hot dry outside air and moist internal body surfaces, a great deal of evaporative cooling takes place there. Instead of expending energy (and water) to cool their entire bodies, these mammals can allow their bodies to heat up to brain-damaging temperatures while their brain's blood stays cool.
The second large vessel that branches from the aortic arch is the left subclavian artery. Note how the branching of the arteries is less symmetrical than that of the veins.
4. Major arteries of the systemic circulation, posterior to the heart (Figs. 8, 9)
Move the internal organs to view the pig’s left kidney area. Pick away the connective tissue to expose the aorta just below the diaphragm and find the coeliac artery. It branches off the aorta to supply the stomach, spleen, and liver. Huh? but the coeliac is so tiny! So the liver, the largest
Figure 7. A. Major veins anterior to the heart.
B. Major arteries of systemic circulation anterior to the heart.
organ in the body, is supplied by a mere branch of a rather small artery! Well, it's more complicated than that. First, the liver also gets blood from the hepatic portal vein (see below). “But that's a vein" you say. And you are correct. But so much blood flows through it ... and the intestines aren't always a super metabolically active organ, so the liver can benefit from it (and it certainly benefits nutrient-wise). The other trick is that despite its size, the liver is not particularly metabolically active. At any given time, only a small proportion of its cells are doing anything. So that, plus the fact that the liver is really weird in having sinusoids rather than proper capillaries, allows it to work as it does.
Just posterior to the coeliac artery, you will find the cranial (superior) mesenteric artery, which supplies the pancreas and small intestine. Watch out! Make sure you find the crescent-shaped adrenal gland before you go digging for the cranial mesenteric artery. Don’t worry. Your pig has two, so you can look at the adrenal on the right later. Also note the lobe of the pancreas situated just ventral to the cranial mesenteric.
At the kidneys, short renal arteries supply blood to the kidneys. At the caudal end of the abdominal cavity, you can see several branches of the aorta. The external iliac arteries are the main arteries of the hindlimbs. The tiny internal iliac arteries, which supply the rectum and hip, can be found where the aorta branches to form the two umbilical arteries.
5. Major veins of the systemic circulation, posterior to the heart (Figs. 8, 9, 10)
In the lower abdominal cavity, find where the external iliac vein and internal iliac vein join to form the common iliac vein. The right and left common iliac veins then join to form the posterior vena cava. Find the renal veins.
6. The hepatic portal system (Figs. 8, 9)
In a normal circulatory pathway, blood takes the following path: artery – capillary bed – vein. In a portal system, the blood travels in the following manner: artery – capillary bed – portal vein – capillary bed – vein. Portal systems are found in many different parts of the body and carry blood from the capillaries of one organ to the capillaries of another organ. In the case of the hepatic portal system, nutrient-rich blood from the mesenteric veins flow into a single mesenteric vein, which joins with the lienogastric (gastrosplenic) vein from the spleen and stomach and becomes the hepatic portal vein. This vein now carries blood to the liver, where it breaks into a second capillary bed. Here the products of digestion pass into liver cells. This ensures that the liver has "first shot" at toxins from the diet as well as glucose, amino acids, and lipids. Capillaries in the liver then converge into the hepatic veins, which empty into the caudal vena cava for transport back to the heart. If the intake of toxins (such as alcohol) exceeds the liver's ability to filter them from the blood, the excess enters the general circulation and on to other organs (like the brain).
Figure 8. Illustration of hepatic portal system depicting associated veins and organs.
Figures 9 and 10. 9. Hepatic portal system. 10A. Fetal and renal circulation. 10B. Posterior circulation.
UROGENITAL SYSTEM
Objectives
1. Identify and describe the function of the excretory system of the fetal pig, noting differences between the sexes and noting structures shared with the reproductive system.
2. Identify and describe the function of the reproductive systems of male and female fetal pigs and trace the pathway of sperm and egg from their origin out of the body.
Excretory System
The bean-shaped kidneys (Fig. 11) perform two functions. First, they continuously remove metabolic wastes from the blood (primarily urea resulting from the metabolism of amino acids in the liver). Second, they monitor and adjust the composition of the blood (particularly water and salts) so that the cells of the body are bathed in a fluid of constant composition. Although the kidneys are situated below the diaphragm, they are actually located outside the peritoneal cavity (dorsal to the parietal peritoneum, the membrane that lines the abdominal cavity). Carefully cut one of the kidneys in half longitudinally (slice it as though you were separating the two halves of a lima bean). Within the kidney, the ureter expands to form a funnel-shaped chamber called the renal pelvis. The dark kidney tissue that you see extending into the renal pelvis is known as medullary tissue (medulla). The outermost portion of the kidney is called the cortex. The cortex contains glomeruli, Bowman’s capsules, proximal convoluted tubules, and distal convoluted tubules. The medulla contains the loops of Henle and the collecting ducts. The medulla is characterized by high solute concentration, so when "pre-urine" flows down the loops of Henle, water flows out of the loops and into the medullary tissue. The net result of this (and a few other processes of the medulla) is that the "urine" becomes increasingly concentrated. In humans, the kidneys filter 1500 liters of blood a day, producing only about 1.5 liters of urine in that time.
Near (but usually not actually on) the anterior/medial edge of each kidney lies a narrow band of light colored tissue, the adrenal gland (adrenal means "near or adjacent to the renal [kidney])". The adrenals may be difficult to see, especially in smaller pigs. Despite it's subtle appearance, the adrenal gland is one of the most bizarre and important glands in the body. The cortex is epithelial in origin; the medulla is neural! In fact, the cortex and medulla are not even united in some vertebrates. The outer layer of the adrenal cortex secretes aldosterone, an important hormone for water balance. The middle cortex produces glucocorticoids like cortisol. These “stress hormones” have a variety of effects ranging from carbohydrate balance to immunosuppression. The inner cortex produces androgens, even in females. These androgens are involved in the growth spurt, development of pubic hair during puberty in girls. The adrenal medulla, being of neural origin, produces norepinephrine and epinephrine (aka adrenaline), which are neurotransmitters. When released, these adrenal hormones produce the fight or flight response, mobilize glucose, and increase heart rate.
The renal pelvis of each kidney drains into a coiled tube called the ureter. The ureters lead from the kidney to the urinary bladder, where urine is temporarily stored. Note the unusual shape (elongated) and location (between the umbilical arteries) of the urinary bladder in your fetal pig. In fact it extends into the umbilical cord! Urine produced by the fetus actually bypasses the urethra (the tube that transports urine from the bladder to the outside of the body). If a fetus urinated in an adult manner, the amnionic sac would soon be fouled with toxic nitrogenous wastes (urea is toxic). Instead, urine produced by the fetus proceeds from the bladder through the allantoic duct and to the allantois (a special sac for nitrogenous wastes). But remember that most nitrogenous wastes are transported to the placenta via the umbilical arteries. However, even in reptiles and birds, the allantois takes on a dual function. In addition to storing nitrogenous wastes, it fuses with the chorion to create a vascularized membrane that mediates gas exchange. In mammals, this latter diffusion function takes place in conjunction with the placenta, as does nutritional exhange and waste removal. In both pigs and humans, the allantoic duct collapses at birth and urine flows from the bladder into the urethra.
To follow the urethra to the urogenital opening, you will have to also examine the reproductive system, as they are linked together. Examine the urogenital system in your pig. Then examine a pig of the opposite sex. You are responsible for both male and female anatomy.
To examine the urethra and the reproductive structures fully, you will need to carefully cut through the pelvis (pubic bone or pubis) of your pig. Don’t make this cut without consulting me. Make sure you keep your cut slightly to the left or right of the midline to avoid cutting important structures.
