Rat Dissection - Lecture notes 13 PDF

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Summary

Lab notes for Bio 102/Zoology 102 taught by Steffenie Widows...

Description

Rat Dissection -

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Latex Injected - Red latex is in blood vessels carrying oxygenated blood - Blue latex is in blood vessels carrying deoxygenated blood Directional Terms

Access to the Body Cavities - When doing a rat dissection, you would start by opening the abdominal cavity - You can see the organs in the abdominal cavity - The diaphragm has been left intact - It is a large muscle that forms a wall between the thoracic cavity cranially and the abdominal cavity caudally - One of the distinguishing features of mammals - Plays a role in ventilation

Respiratory System - General Functions - Ventilation - Bring air into (inhalation) and out of the lungs (exhalation) - Gas exchange

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Oxygen and carbon dioxide are exchanged between air and blood in the many tiny air sacs called alveoli Parts of the Respiratory System - Diaphragm, Nasal Cavity, Pharynx, Epiglottis, Larynx, Trachea, Bronchi, Bronchioles, Alveoli

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Pharynx and Epiglottis - Functions - Pharynx - The back of the oral cavity and nasal cavity meet at a space called the pharynx. The pharynx is a passageway for air entering the trachea and food entering the esophagus. This makes it part of the digestive and respiratory systems - Epiglottis - It is a cartilaginous flap that sits on top of the trachea. During swallowing, the epiglottis covers the top of the airway leading to the lungs so that food and liquid cannot enter

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close-up of oral cavity, lower jaw has been pulled back. The palate is the wall between the nasal cavity and oral cavity Diaphragm and Trachea - Functions - Diaphragm - A muscle that separates the thoracic cavity (location of the lung) and abdominal cavity; it contracts creating lower pressure in the lungs and air enters, it relaxes creating higher pressure in the lungs and air exits - Trachea - Passageway for air from pharynx to bronchi; it has cartilaginous rings embedded in the in its walls which keeps this passageway open all the time - The tube that runs down the middle of the thoracic cavity from the neck to the lungs - Near the heart, the trachea splits into right and left bronchi that enter the lungs - Lungs

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Composed of millions of tiny air sacs called alveoli that are site of gas exchange between air and blood

Lungs and Intercostal Muscles - Identifying the Lungs - Lungs lie on both sides of the heart. They are reddish brown color in the preserved rat - The lungs are divided into sections called lobes - They have a “spongy” texture - Intercostal muscles are between the ribs. During inhalation, they contract and raise the ribs, which increases the volume

Inverse Relationship between Volume and Pressure - Inhalation - In order for air to enter lungs, the pressure in the lungs must be lower than the pressure outside - Increase volume in lungs by contracting diaphragm - Decreases pressure in lungs - Air flows from higher pressure outside to lower pressure inside

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- Diaphragm contracts, flattens - Exhalation - In order for air to leave the lungs, the pressure in the lungs must be higher than the pressure outside - Decrease volume in lungs by relaxing diaphragm - Increases pressure in the lungs - Air flows from higher pressure inside to lower pressure outside - Diaphragm relaxes, becomes dome-shaped Digestive System - General Functions - Process food mechanically and chemically to prepare it for absorption - Absorption-digested nutrients move from digestive tract to blood or lymph circulation (absorption) - Eliminates, as feces, anything that could not be chemically digested - Digestive Tract - Series of organs through which food and feces pass - Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine - Accessory Organs - Organs that play a key role in digestive processes, but are not part of the digestive tract. Therefore, food does pass through them. They secrete into the digestive tract through ducts - Salivary glands, liver, pancreas - Salivary Glands - Function - Secretes digestive enzyme that begins the chemical digestion of carbohydrates, such as starch which is composed of long chains of glucose - The salivary enzyme breaks starch into smaller chains of glucose - Salivary Glands - Located between the skin and jaw muscles. Just below the jaw, in the neck region, you can identify the salivary glands

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Hard Palate and Soft palate - Functions:

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Pharynx and Esophagus - Functions - Pharynx - Passageway for food from mouth to esophagus - Esophagus - Muscular tube transport food from pharynx to stomach - Located dorsal to trachea - Passes through the diaphragm and connects to stomach

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Hard Palate - Forms roof of mouth, separates mouth cavity and nasal cavity, aids in mechanical digestion, is composed of bomne Soft Palate - Extends caudally from hard palate as continuation of roof of the mouth; during swallowing it moves up to block food or liquid from going into the nasal cavity, it is composed of muscle Identifying - Hard palate is bony and has ridges - Soft palate is muscular and smooth

Liver

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Functions - Liver - Produces bile and secretes it into the duodenum (first part of small intestine - Bile is not an enzyme, it does not chemically modify lipids, it breaks up large globules of lipids into smaller globules which increase surface area for digestive enzymes to work Identifying - Large reddish brown multi-lobed organ located just caudal to the diaphragm, majority of it is on the right side of the body

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Stomach - Functions - The stomach has multiple layers of muscle for mechanical digestion - Chemical digestion of proteins begins in the stomach; proteins are long chains of amino acids, the stomach secretes a digestive enzyme that breaks protein into smaller chains of amino acids - Identifying - The stomach lies on the left side of the body. It is curves as the diagram shows - The liver is lifted out of the way to see the esophagus pass through the diaphragm and join the stomach - The pyloric sphincter is a muscular valve that controls the passage of food from the stomach to the small intestine. - Diagram shows the empty stomach has folds. This fits the function of accumulating food before letting it continue on in small portions of the intestine by allowing it to expand

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Small Intestine - Functions - Secretes digestive enzymes that complete chemical digestion of protein and carbohydrate; absorption of digested nutrients into blood or lymph circulation; receives secretions from liver and pancreas; it is longer than the large intestine, but smaller in diameter - 3 parts = duodenum, jejunum, ileum - Identifying - First part of the small intestine is attached to the stomach. It ends where it connects to the cecum, a large blind pouch.

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Absorption - The inner wall of the small intestine has a velvety texture - This texture is due to the finger-like folds, called villi, on the inner surface - In addition, each cell has folds called microvilli. These cells secrete enzymes that complete carbohydrate and protein digestion

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Increased surface area for increased absorption Each villus contains a blood capillary and a lymph capillary (a lacteal) - Protein → amino acid; in small intestine, absorbed into blood capillary -

Carbohydrate → glucose; in small intestine, absorbed into blood capillary

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Lipid → fatty acid and glycerol; in small intestine, absorbed into lymphatic capillary

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Pancreas

After a meal rich in fat, the intestinal lymph vessels appear as fine white lines because they are packed with absorbed fatty acids The lymph with the fatty acids circulates through the lymph vessels and eventually movies into blood circulation at the Left Subclavian Vein

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Function - Secretes digestive enzymes for protein, carbohydrates and lipids into small intestine - The pancreas is a diffuse organ (looks like chewed gum thinly spread out) - Located along dorsal side of stomach, between the duodenum and the spleen - The diagram shows that the duct carrying bile from the liver and duct carrying digestive enzymes from the pancreas both secrete into the small intestine (duodenum) - Rats do not have a gallbladder

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Cecum and Large Intestine (colon) - Functions - Cecum - Contains microorganisms that digest cellulose (plant cell walls) - Large Intestine - Absorbs water and some vitamins; undigested material is expelled as feces - Identifying Cecum - Large blind pouch at end of small intestine - Identifying Large Intestine - Located from cecum to anus

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Summary

Urinary System - Helps maintain water balance and selectively removes waste produces and excess salts from the body - The blood is filtered in the kidneys and as the filtrate flows through the kidney some of the substances are reabsorbed - Additional substances that the body needs to get rid of may also be secreted into tubules. The filtrate that leaves the kidneys is urine. - The urine flows into ureters, is stored in the bladder, and transported to the outside by the urethra

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Circulatory System - The primary function is transport of nutrients, oxygen, hormones, waste products and elements of the immune system

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Arteries - All arteries transport blood away from the heart - Most carry oxygenated blood and are shown as red in images, there is one that carries deoxygenated blood - Have thicker walls than veins because they carry blood that exerts more pressure on them - Aortic arch, common carotid, subclavian, descending aorta, renal artery, common iliac Veins - All veins transport blood to the heart, most carry deoxygenated blood and are shown as blue in images, there is one that carries oxygenated blood - superior/cranial vena cava, inferior/caudal vena cava, renal, common iliac Heart and Major Blood Vessels

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Auricle: small, cone-shaped, muscular pouch that projects from the atrium. Both auricles help their respective atria hold more blood, and in this respect, they essentially serve as reservoirs. Major Vessels of Abdominal Cavity - Arteries branch off of descending aorta which is now seen in the abdominal cavity. Veins drain into the caudal vena cava

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Comparing walls of right and left ventricles - Left ventricle wall is thicker. Left ventricle is pumping blood to all of body except lungs, right ventricle is pumping to nearby lungs. So, left ventricle needs to have more muscle. The Hepatic Portal Vein - Carries blood from the small intestine to the liver. The blood is low in oxygen but rich in Glucose and Amino Acids which have been absorbed in the small intestine - Reddish brown color -- pin lifting up

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Review

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Male and Female Reproductive System - Male Reproductive System - Functions of Scrotum, Testes, Epididymis, Ductus Deferens

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- Scrotum: pouch of skin contains testes - Testes: produce sperm - Epididymis: where sperm cells mature and are stored - Ductus deferens: transports sperm from scrotum to the urethra Identifying - Testis = large oval organ - Epididymis = comma-shaped, partly surrounds the testis, begins at the cranial end of testis and then becomes thinner as it continues down the side - Ductus deferens = tube that continues cranially from “tail” of epididymis into the body, and behind the bladder where it joins with the urethra

Functions of Seminal Vesicles and Prostate - Add secretions to semen that help to energize and activate sperm, suppress female immune responses, and help increase the chance of fertilization Identifying - Seminal vesicles - two glands on each side of the bladder, edges looks scalloped - Prostate - immediately caudal to the bladder Functions of Urethra - Transports seminal fluid with sperm outside the body - Urethra is difficult to observe - The penis is located in a pocket of skin - Observe urethral opening in tip of the penis

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Female Reproductive System - Functions - Ovaries = production of eggs - Oviducts = transports eggs to uterus, site of fertilization - Uterine horns = embryo development - Vagina = birth control - Identifying - Ovaries = small, oval organs lie slightly caudal to kidneys, may be partially obstructed by fat which should be removed - Oviducts = small, coiled ducts extending from ovaries; need to use dissecting microscope to see - Uterine Horns = Y shaped organ, each horn is a continuation from the oviducts. May have embryos in them. In humans the horns are fused to form a single uterus - Vagina = the uterine horns unite caudally to form the vagina

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