FROG DISSECTION Biology 1110 Lab 5 ReviewSupport Material

FROG DISSECTION Biology 1110 Lab # 5 – Review/Support Material

Frog Dissection This presentation is not intended to replace the dissection lab exercise. The purpose is to assist you if you are dissecting on your own, or to help review your understanding, and prepare for the lab practical.

Anatomical Requirements of the Dissection The dissection will emphasize the general anatomy of this vertebrate. The 26 required items are seen in the diagram and listed in the next slides. Although there will be some discussion regarding the physiology (function) of observed structures, physiology is not intended to be emphasized in this exercise.

Dissection Requirements

Frog Dissection EQUIPMENT REQUIRED. PRESERVED FROG

Opening the body cavity for observation This diagram demonstrates the cuts that are to be made in order to open the body cavity. The cuts are made twice, first through the skin and then through the entire body wall.

Frog Dissection The initial cuts are illustrated on this frog. When making any cuts an upward pressure prevents damage to underlying structures.

The first cuts through the skin have been made and the skin has been pinned back. A close look at the skin reveals the significant vasculature (blood vessels) in the skin. The frog exchanges respiratory gases utilizing a pair of lungs and the moist skin.

The second cuts are made through the abdominal wall and thoracic (chest) wall. The final cuts required to open the body cavity are animated.

The body cavities have been successfully opened. You are now ready to begin your observations. Two dissected frogs will be used to complete the dissection requirements.

Dissection Requirements. � By clicking the forward ( ) and backward ( ) button you can jump from this requirement list to the appropriate picture(s) and then back to the list. We will not cover the requirements in the order previously presented. Liver – the largest organ in the abdominal cavity. Heart and surrounding pericardium. Lungs – a pair located in the thoracic (chest) cavity Brachial nerve – a large nerve servicing the upper extremities.

Gall Bladder and bile duct – check under the liver. Stomach – In the abdominal cavity; C-shaped. Pancreas – small strap of tissue within the stomach’s “C” Intestine – trace from the stomach; small and large portion. Peritoneum - the lining of the body cavity Mesentery - abdominal tissue supporting numerous organs. Spleen – lymphatic tissue found within the mesentery.

Kidneys - a pair of organs within the abdominal cavity. Testes – primary sex organs of the male Ovary – primary sex organ of the female Oviduct – delivers the egg cell to the external environment. Urinary Bladder – stores the urine produced by the kidneys. Skeletal muscle - contraction moves the skeleton Tendon/tendon of Achilles – tendons attach muscle to bone. Long bone (femur) cut to demonstrate marrow cavity Sciatic nerve - the largest nerve in the body.

Liver The liver is a large, multi-lobed organ found within the abdominal cavity. In addition to being a major detoxifying organ, the liver produces most of the plasma proteins, & stores valuable commodities. The liver also produces the bile that is stored in the gall bladder, and used in the digestion of fats.

Heart and Pericardium The amphibian heart is a three-chambered heart. Your heart has four chambers. The heart resides within the pericardium, a sac-like structure that contains lubricating pericardial fluid. Both pictures clearly demonstrate the heart and pericardium. The forceps in the right picture is holding the tissue of the pericardium.

Heart and Pericardium Additional pictures of a frog heart residing within the thoracic (chest) cavity, and contained within the pericardium.

Right and Left Lung The pair of lungs is also located deep within the thoracic cavity. Amphibian lungs are rather sac-like with much less surface area than mammalian lungs. As a consequence the amphibian lung is not as efficient. Gas exchange through the skin helps make up for this inefficiency. It also explains why almost all amphibians must keep their skin moist. Head

Brachial Nerve A brachial nerve can be seen entering each of the frog’s forelimbs. The brachium is the upper area of each limb.

Gall Bladder and Bile Duct In both pictures the liver has been reflected back so as to reveal the somewhat spherical, green gall bladder. The gall bladder stores the bile produced by the liver. The bile is then delivered via the bile duct to the small intestine. Bile functions in the digestion of fats. He ad Liver lobe He ad

Stomach The stomach is a food storage organ and is involved in the digestion of proteins. When stomach processing is complete the material is released into the small intestine. He ad Stomach

Pancreas The pancreas produces a variety of digestive enzymes that are delivered into the small intestine. The pancreas also produces a couple of hormones involved in sugar metabolism. One of the hormones is insulin. In the frog, the pancreas is a thin tissue strap located within the “curve” of the stomach.

Intestinal Tract The small intestine is of considerable length and is involved in the digestion of food and absorption of nutrients. The larger portion of the intestinal tract is identified by the probe in the picture on the right. Intestinal tract

Peritoneum The peritoneum is the smooth, moist lining of the body cavity. It composed of simple squamous epithelium (studied earlier). Peritoneum

Mesentery The mesentery is made of the same tissue, and is connected to the peritoneum. The mesentery is a double layer of this tissue and invests many abdominal organs as seen in both pictures. Lifting the digestive tract reveals the extensive nature of the mesentery. This tissue has numerous functions.

Spleen When the digestive tract is lifted, and the mesentery demonstrated, a structure within the mesentery becomes obvious. The spleen is pointed out in both pictures. The spleen is part of the lymphatic system. One important function is in the breakdown and recycling of worn out red blood cells.

Kidneys The pair of kidneys, in the process of urine formation, remove waste products, help maintain acid-base balance, electrolyte balance and water balance. The kidneys are located against the back body wall in the abdominal cavity. In the pictures below they are the brown structures identified. Left kidney Right kidney

Gonads – male testes The primary sex organ of this male frog are the testes. The right testicle is pointed out in both pictures. The testes produce the male gametes (sperm cells) that will fertilize the female egg cells. You can see their location close to the kidneys. Right testicle

Gonads – female ovary and oviduct The female frog in the picture below demonstrates a condition of reproductive inactivity. The ovary is the primary sex organ, and produces the gametes (egg cells). The oviduct is also demonstrated. Ovary Oviduct

Urinary Bladder The urinary bladder stores the urine produced by the kidney. In the picture the forceps is demonstrating the urinary bladder.

Skeletal (Striated) muscle and Tendon The frog’s right leg has been skinned in order to demonstrate the large swimming and jumping muscles of the leg. Tendons attach skeletal muscles to the bones of the skeleton. When the muscle contracts the force is transferred through the tendon to the bone, causing movement. Tendon of Achilles is demonstrated

Cross-section of long bone (femur) demonstrating marrow cavity. In the pictures we see that the femur has been cut. The picture on the right demonstrates the presence of the marrow cavity within the bone.

Sciatic Nerve The largest nerve in your body is the sciatic nerve that services the lower extremities. It is demonstrated in both photographs. Click arrow to continue to the frog model