EXERCISE 3 Avian Organ & Organ System

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1 BI-160 LAB REPORT #3 NAME Introduction EXERCISE 3 Avian Organ & Organ System To investigate the major avian organs and organ systems used to sustain a bird and its active lifestyle, you will complete a variety of exercises. While you are completing these exercises, keep track of the amount of time you spend on each. You will be asked at the end of this lab to estimate the total amount of time it took you to complete this lab. EXERCISE 3.1 The Avian Digestive Tract The avian digestive system is specialized to process unmasticated (not chewed) food since they lack teeth. The major parts of this system the oral cavity, esophagus, crop, twochambered stomach, liver, pancreas, and intestines are further specialized to accommodate particular types of diets and feeding practices. The Oral Cavity houses the tongue and soft palate. The soft palate has taste buds and tactile sensory receptors which allow the bird to taste and feel what is in the mouth. Most birds have rear-directed projections on their tongues called Papillae that aid in swallowing. Bird tongues usually are not muscular structures like ours, but rather work on a tendon system much like a rope-and-pulley system. The shape of a bird s tongue also greatly reflects its diet. Use the diagram on the following page to guess the function of each tongue type by matching the letter of the tongue to the type of diet. food-straining generalized for seeds probing & spearing insects nectar-feeding fruit-eating fish-eating

2 Since birds don t have teeth and the ability to chew their food, they must swallow it whole. Some birds can tear and crush but most simply swallow whole food items with the aid of saliva to lubricate its passage. In most birds, food passes from the mouth to the pharynx and then to the stomach via the esophagus, a muscular structure lined with lubricating mucous glands. In birds that swallow large food items (like fish) or store large amounts of liquid (like nectar), the esophagus is highly distensible. The esophagus can in some birds be inflated for display and sound resonance. Passage of food through the remainder of the digestive tract from the esophagus through crop to the glandular stomach (proventriculus) and gizzard into

3 the intestines and finally out the cloaca as feces- varies from less than half an hour in the case of berries ingested by thrushes to half a day or more for less easily digested food. Each stage in this passage may include special processing. The sections of the digestive tract are adapted to the specific requirements of a bird s normal diet. Correctly match the function to the corresponding digestive structure in the following exercise. Esophagus Crop Stomach Gizzard Intestines Cloaca a. may contain pebbles to aid in grinding up food items b. glandular walls aid in digesting protein (muscle) c. organ for storage and moistening d. distensible organ to transport food from oral cavity e. digestion of carbohydrates & absorption of food f. location where indigestible food is eliminated Though each of the above organs typically function the same in most birds, some are modified to the specific needs of the bird species. For instance, birds that eat fruits or nectar by-pass the crop (or don t have one), stomach, and gizzard to allow for quicker digestion and absorption in intestine. The gizzards may be thin-walled if not needed or exceptionally thick walled to crush hard items like ingested seeds. EXERCISE 3.2 The Avian Respiratory System The bird respiratory system is perhaps the most effective known. This is because air passes though the lungs as well as being stored in large air sacs located within the body cavity. Thus, there is never stale air in the actual lung of the bird. Four anatomical features the nostrils, tracheal system, lungs, and air sacs shunt air between the outside and the insides of the bird in a Unidirectional Flow (one-way flow). As a result, the avian respiratory system is extremely efficient. Study the diagram on the following page of the bird s respiratory system and answer the following questions. 1. Following one breathe, name the structures in order as the air moves through the respiratory system. Begin and end at the Main Bronchus (the air pathway leading to and from the Trachea and Nostrils) Main Bronchus

4 1. Which set of air sacs contain air that is high in Oxygen? 2. Which set of air sacs contain air that is low in Oxygen?

5 3. How many breathes does it take to complete a respiratory cycle (the complete pathway from inhalation to exhalation)? 4. What advantages does having air move in one direction through the lungs give a bird? AIR SACS Not all air sacs aid directly in respiration. The number air sacs also varies from six in House Sparrows and seven in the Loons and Turkeys to at least twelve in shorebirds and storks. Most birds, however, have nine air sacs: 1. Paired Cervical Sacs located in the neck, may aid in inflating throat pouches in birds such as Sage Grouse and Frigatebirds 2. Pair of Anterior Thoracic Sacs fill the forepart of the body cavity, aid in respiration 3. Pair of Large Posterior Thoracic Sacs fill the upper chest, aid in respiration 4. Pair of Large Abdominal Sacs cushion the abdominal organs & carry air to pneumatic leg and pelvic bones 5. Single Interclavicular Sac branches penetrate the wing bones, sternum, and syrinx (the voice box of a bird) If not all air sacs are directly involved in Respiration, what other functions may they have?

6 EXERCISE 3.3 The Avian Excretory System Birds, like mammals, are Endothermic ( warm-blooded ). Since they have relatively high body temperatures, they spend large amounts of energy and water cooling the body. This may become a problem for species that live in dry arid environments where water is limited. Most birds have several adaptations to limit water loss. They keep their bodies osmotically balanced by using a combination of strategies: 1. Capture Metabolic Water water is generated each time organic molecules are broken-down. Birds are able to produce more metabolic water in relation to body size than do most vertebrates. For example: a. Metabolism of 1 gram of Fat yields 1.07 grams of Water b. Metabolism of 1 gram of Carbohydrates yields 0.56 gram of Water c. Metabolism of 1 gram of Protein yields 0.40 gram of Water 2. Capture Water from Food water taken directly from the food varies with the type of food. Birds of prey satisfy most of their water needs from the body fluids of their prey. This is true of most carnivorous birds (meat-eaters, insect-eaters, etc) as well as granivorous birds (seed-eaters) and herbivorous (plant-eaters). 3. Drink Free-Water just like us, find a source of water and drink up! 4. Limit Water Loss (Kidney) the most conspicuous adaptation for saving water is the formation of a metabolic waste product (nitrogenous waste product) known as Uric Acid. The break-down of proteins produces nitrogenous products in the form of Ammonia, which become toxic when accumulated. Animals such fish who live in aquatic environments can simple drink large amounts of water to keep the toxin diluted and release the Ammonia out of the body quickly. Land-based animals don t have this advantage so must spend energy to convert the Ammonia to less toxic forms. Mammals convert the Ammonia to Urea, a less toxic form which requires less water to keep it diluted. Birds, however, convert the Ammonia to Uric Acid, a semi-solid suspension which is nearly non-toxic. Birds require only 0.5 to 1.0 milliliters of water to excrete 370 grams of Uric Acid compared to Mammals who require 20 milliliter of water to excrete the same amount of Urea. Birds can concentrate their uric acid levels in the Cloaca to 3000 times the acid level in their blood. The most efficient mammals (Kangaroo Rats) can only concentrate urea to levels 20 to 30 times those in the blood. 5. Limit Water Loss (Behaviorally) like other animals, birds can limit water loss by seeking shade, burrowing or perching in a cave (or other humid chamber), become active only in the cooler parts of the day, or become completely nocturnal. While minimizing water loss is important, a bird also wants to minimize the total amount of water kept in the body. Birds do not have a urinary bladder to store urine like mammals and hence any urine produced flows directly out the Cloaca. The Cloaca serves dual functions: it

7 combines the urine with the fecal material (undigestable material) from the digestive tract and releases a white/gray paste known as Guano. 1. What Advantage does not having a Urinary Bladder have for birds? 2. Choose one specific species of Bird and describe the different strategies it may use to limit its loss of water and be more efficient at excreting its waste products. Bird Species: Adaptations: EXERCISE 3.4 Integration of Systems You ve now studied only a couple of avian organ systems, but each plays an integral role in maintaining the necessary metabolism needed to sustain flight and an active way of life. For each of these organ systems, list some ways each system aids in maintaining flight and an active life style. Avian Digestive System: Avian Respiratory System: Avian Excretory System: Estimated Time to Complete this lab