in this video we will be studying the anatomy of the common Norwegian rat ratus norvegicus the Norwegian rat is commonly used in studying uh comparative anatomy of vertebrates and this is because uh it displays all the typical Maman body plants that we would see with all the other uh mammals that you would study in other words uh what you're going to learn by dissecting the rat is going to be broadly applicable to most of the other mammals now let's begin with the external Anatomy the first thing we'll notice is that right up here in the ear area we have the paina and this is that flaplike external ear and it's going to direct the the sound right into that ear canal called the um external auditory Miatas when we look at the eyes uh one of the things I want you to notice about the eyes is that they are well formed and that you'll have an um upper and a lower eyelid but if we spread those apart and we look and towards the Corner we're going to see the nting membrane inside that corner area of the eye and it's used to protect the eye the whiskers are going to be long and stiff on the hair and they're going to have a a tactile or sensory function and these are uh known as the uh uh VI then we'll have our external naries and um as we uh begin uh our further uh study of the Rat uh don't forget that several words will be used to indicate the location of organs and structures within the body so that the cranium is going to be towards the head uh the coddle area will be towards the tail area the dorsal will be the uh back side the ventral will be the belly side lateral will mean towards the sides medial will mean towards the middle line proximal will be nearer or closer to uh the Bas of structure where distal will be further from the uh base of structure and when we talk about proximal and distal this is in relation to some other structure so if we were to look at this and we'll call this the elbow and the the fingers and then this is that Bas of structure we would say that this elbow region is proximal to the fingers meaning the elbow area here would be closer to this point of attachment where the fingers would be distal to the Elbow meaning that they are further uh from the elbow to the point of attach ment now the rat does not have an elbow but we're just using that to explain this terminology now here we've laid the rat on its uh dorsal surface or its back and we have the ventral or belly side showing now this is a male but uh present in females only we would have the mammary Papa or the nipples there's generally six on each side there would be three in the uh chest area and three in that um abdominal area on the females only now this right here is showing us the uh female eurogen uh structures and so in the female there's going to be two openings uh close together in front of the anus where the male would only have one the most anterior which would be this one right in here is going to be the uh urethal orifice and it leads to the urinary structures the urinary system this one right in here is the vaginal orifice and it's the extra opening of the reproductive system and so it's going to lie more posterior to the urethal orifice now over here we have the male and with the male urogenital structures uh the reproductive uh products and the urinary products uh this is all going to be uh in the tip of the penis and the penis is usually hidden inside of fold of skin and so uh it would be a little difficult for us to see on this diagram uh the testes located right in here are going to be housed in that large pouch called the scrotum and uh the testes would be uh if the male is in breeding season would be enlarged and if they're not in breeding season would be smaller now here we have the skeletal system of the rra and the bones that you see on the wrap will mirror the bones you would see on other mammals and we'll begin with the skull now the skull is the cranium it is composed of quite a few other bones and they're going to be the same bones that you would see in the human or the cat or any other uh mammal that you may study so we would see the the parietal bone up here at the top and we would see the frontal bone over here um you would have your incizors now in the rat they are continuously growing throughout the life cycle of the Rat and that's why the rat's gnaw is to uh wear the the bones down uh you would see the zygomatic Arch which would be in this area here the maxil is the the top U of the U the jaw the lower jaw area right here is the mandible uh we would get to this area back in here we would see the oipal bone we would see the uh temporal bone right in this area and um you would have this opening right in there which is the external auditory meatus or the opening for the ear moving back the uh vertebrae of the the neck or the cervical vertebrae the very first one is the Atlas the second is the axis the remaining ones are just known as cervical vertebrae the vertebrae that's located in the area where the ribs attach are the thoracic past those we get into the lumbar vertebrae and then finally we would get into the uh the sacrum and the coxis we have the scapula uh being the shoulder blade up front the collar bone would be the clavicle the upper bone of the forearms are the humorous down here we have two bones the radius and the Onna the radius would be on the thumb side the Onna would be the opposite we'll get into the carpal the metacarpal and the fanges moving back the upper leg bone is the femur the knee bone is the patella there are two bones in the lower leg the larger is the tibia the smaller is the fibula we get into the tarsals the metatarsals and the fanges when we get into the hip area we have um the tailbone right in this area being the sacrum here we have the ilium we have the pubis being this front portion the ishum this all makes up that pelvic area and then we get into those coddle vertebrae now as we begin the muscular system of the Rat first off know that all of the muscles are attached to at least two different structures and that's usually bone but occasionally it can be soft tissue when the muscles contract one of these attachment points will move while the other one will remain stationary the point that moves is the insertion and the point that does not is the origin now we will not be able to cover all the muscles on the the wrap but we will hit some of the main muscles uh of the Rat musculature we'll begin with the gastrus the gastrus is the main calf muscle now it is attached to a tendon called the um Achilles tendon and that's attached down to the the tels and if one was to tear that it would uh cause the entire gastro St nemus muscle to be inoperable moving on up we have the uh the tibialis this is also known as the tibialis Andor uh this one right here lays on top of the tibia the um tibia would be the insertion and then one of the tarsals or one of the metat tarsals would be its origin and it allows it to flexx the foot okay here we have the external oblique now this is a broad thin sheet that covers most of the lateral and ventral part of the abdomen this compresses the abdomen and helps to hold those internal organs in place now underneath the external oblique we have this um this thin uh muscle known as the rectus abdominis and again this also compresses the abdomen and helps to hold those internal organs in place right in this area here we have the latissimus dorsai and this is a wide flat muscle it's posterior to the shoulder and this muscle right here uh is what pulls the arm codul and uh this right here it's insertion is going to be the humoris right over in this area we have that Stern midus this muscle is the one that when it contracts it rotates the head down and right here not labeled but we have the sternal hyoid it's a narrow band of muscles along the midline it's uh um the bone that pulls the highway bone back and it's the support that's beneath the base of the tongue now here we've taken the the rat and we've laid it on its belly and we're looking at the the dorsal surface or the um the back and we can see that external oblique wraps around from the ventral surface over to the um the dorsal surface and right here we have that spinal deltoideus and the spinal deltoideus is what pulls the scapula back and it pulls the scapula forward and away from the ribs in the humans this would be the deltoid muscle it's also typically in humans the sight of a lot of injections or shots right in this area we have the gluteus superficials uh this right here covers much of that anterior hip region and when we look at this muscle right here it includes the gluteus maximus the Sartorius which is the longest muscle of the body the tensor falate and you would find these on other mammals of course the purpose of the this gluteous superficial is to pull the thigh outward and then right in here we have the biceps florus which is a very large muscle it's posterior to that gluteus and uh it pulls the leg out or it flexes that lower leg now here we've taken the rat and we've laid it on its side and you can see that spinal deltoideus that we've just spoken about and here we have the very large triceps brachi muscle triceps brachi is because it has three major parts a lateral a long and a medial head and then up above in this area here we would have the biceps Brach ey right here we have the seratus or the shus interior muscle this is typically known as The Boxers muscles up around this area we have the temporalis muscle associated with the temporalis bone the masser is right in this area these are those large cheek muscles and the origin is going to be on the uh cheekbone or the zygomatic Arch and then the maxill and these if you were to grit your teeth you would feel the massit or muscle and so this one is the the major muscle for uh closing and for chewing right in this area we have the uh ACO uh trapezius muscle now this muscle right in here is what pulls the scapula Inward and and closer to the ribs and upward closer to the back of the uh the backbone okay so we can see the M bone again with this view we can see that latissimus dors side here's that biceps we were talking about in relation to the uh the large triceps we can see one of the main uh veins of the body the external jugular vein and then right in here we have the in costals the intercostals are the muscles that run in between the ribs and these help with uh breathing and while these are not anywhere near all the muscles of the the rat they do give you an idea of some of the main muscles that you would see during the typical dissection as we begin the um internal anatomy of the uh the rat we will begin with the um the throat area and we can see the the roof of the mouth that hard palet moving back we would move to the soft pallet right here we would see the uh the tongue and we can see see those incizors in that external naries moving on down we can see the uh the thymus and we can see the uh the heart the heart being four chambered on either side of the heart we have the uh the lungs below we have the thin uh musculature uh of the diaphragm we can see that since the thymus has been removed in this area we can see the trachea and we can see those cish Rings behind the tracha here we have the esophagus moving on down we can see the thymus uh right in this area we have the heart it is for chambered The upper chambers are the Atria the bottom is The ventricle we can see that diaphragm right in this area just a really nice view showing you how that trachea is in front and then how the um right behind it we would have the um the esophagus moving down it Remains the trachea until they break Branch once they Branch they become the primary bronchial and they would enter into the uh lungs so again we would see the esophagus and we would see the trachea moving down we've got that thymus sitting on top of the heart here's our heart The upper chambers are the atrium we can see uh the right atrium the lower would be the ventricles uh we can see one of the lungs located right here and this area right across here we would have the diaphragm below the diaphragm we get into the abdominal cavity the largest organ of the body is the liver now on most mammals if we raise the liver up we would see the uh gallbladder however unlike most mammals the um rat does not have a gallbladder for storing its bile so here we can see the rib cage again the diaphragm would be in this area we have the um liver right here we have the stomach it is j-shaped if we were to raise the stomach the grainy uh gland that we would see underneath would be the pancreas right in here we can see the spleen moving on down from the stomach we would have a valve called the pyloric valve and it would uh open up into the small intestines the small intestines are divided into three regions the duodenum is a section attached to the uh stomach the middle part is the gunum and the last part is the ilum and it would open into the large intestines or the colon now the junction right next to the small intestines where we have the the large that is the the seeum so right here we can see just the typical part of the large intestines this um has the urinary bladder located right in here uh being a female we can see the ovary and running from the ovary down into the uterus which is where the the two um Fallopian tubes meet we would have the horns of the uterus so this tube going from the ovary down to the uterus is the fallopian tube or um the uterine tube now the thin tissue that helps to hold the organs in place and is very easily seen in between the small intestines is the mesentary over here we can see the kidney sitting on top of the kidney is the adrenal gland notice its location with regard to the spleen the main um vein of the body is the inferior vnea the main artery of the body is the abdominal aorta or the descending aorta again we can see those kidneys now the kidneys are behind the peronal cavity so they're known as being retrop peronal we can see the um abdominal aorta we can see the inferior vena here uh notice that going from the kidneys down until we get uh down to the bottom with the urinary bladder we have a tube and this is known as the urer now here we have the uh anatomy of the um the male wrap and we can see that scrotal sack and right there the penis and if we were to cut this open we would be able to see the testes and sitting on top of the testes is the epidemis and then running from the the testes over we can see that uh vast deine in this area right here just another view showing you the vast deine and its location with regard to the uh urinary bladder finally just uh one additional view showing the uh internal structures of the Rat where we can see the heart and we can see the trachea um the liver again remember that the uh Rat does not have a gallbladder we can see the small intestines we can see the stomach we can see the seeum the um seminal vesicles the vast defrin the testes with the epidemis on top we can see the uh urinary bladder the kidney is not present uh well here it is here's the kidney right there and running from the kidney down to the bladder we would have the urer remember that the kidney is uh retrop perianal and so just one additional overview of the body and we can see those lungs right there and in this view again we can see the liver and we can see the lungs and that four chambered um heart and the trachea remember that the esophagus is behind the trachea uh we can see the uh small intestines and the seeum we can see the large intestines here we can see the graany uh pancreas that is underneath the stomach stomach being raised uh we can see the the bladder um so um again just go through make sure you can identify all of these key organs on the uh the rat