Lab 1: Rat Dissection Flashcards
List the main internal differences between rats and humans.
Teeth
Gall bladder
Reproductive system
How are the teeth of rats different to those of humans?
Adapted for gnawing. The paired incisors grow throughout life and lack enamel on their posterior surfaces, so that rapid wear of the posterior surface produces a characteristic chisel shape. Rats do not have canines because they are herbivores.
How do the jaws of rats differ from humans?
The lower jaw (mandible) is in two pieces, hinged in the middle. The spacing between incisors can be varied at will.
At what age are rats full grown? What is their life span?
6-8 months
3 years
How do the fore and hind limbs of rats compare to humans?
Both have pentadactyle fore and hind limbs.
Compare the tails of rats and humans.
Rats use their tails for balance. Human embryos possess a distinct tail but do not retain it through fetal life.
What is special about rat nostrils?
The nares can be closed under water.
How are the long hairs on the faces of rats useful?
The vibrissae are tactile organs which allow the rat to navigate confined spaces in the dark.
Describe the genitalia of male rats
The scrotum, which contains the testes is seen near the anus. Anterior to this is the prepuce, a skin fold concealing the glans of the penis.
How are male rat genitalia different to that of other primates?
In primates the penis is external tot he body wall for most of its length but in rats, the flaccid penis is contained within the abdominal wall.
Describe the genitalia of female rats.
Vaginal opening is in front of anus. Urethral opening is on the tip of a papilla anterior to the vagina.
What is meant by a papilla?
A small, rounded protuberance in a part or organ of the body.
Which membrane is bonded to the abdominal wall? What does it surround?
Peritoneum surrounds the peritoneal cavity.
What is the name of the peritoneum covering the abdominal wall?
Parietal peritoneum
What is the parietal peritoneum continuous with? What does it do?
A double layer of peritoneum called a mesentry. It suspends the intestines.
What is the name of the peritoneum covering the intestine?
Visceral peritoneum
What are the four ventral body cavities?
Peritoneal cavity
Two pleural cavities
Pericardial cavity
What type of organ is the thymus gland? What is its function?
Lymphoid organ which has a role in the formation of T-lymphocytes. Also secretes hormones important in the development of other lymphoid tissues.
Why is the gut tube long?
In order to increase surface area for absorption and secretion.
What are the three tubular portions of the gut?
Oesophagus, small intestine, large intestine
What are the two sacs of the gut?
Stomach and caecum
What happens to the contents of the gut in the sacs?
It temporarily comes to rest.
Where does absorption and secretion occur in the gut tube?
Everywhere downstream of the oesophagus.
What other structures secrete into the gut?
Two large glands (liver and pancreas)
Which side does the stomach mostly lie on?
The left side
What are the two types of curvature?
Greater and lesser
Where does the oesophagus enter the stomach?
Part-way along the lesser curvature.
What are the dimensions of the small intestine?
Uniform diameter
Four body lengths from inlet to outlet.
What are the three regions of the small intestine?
Duodenum, jejunum and ileum entering the caecum
What is the small intestine attached to the dorsal body wall by?
A transparent mesentery which is a double-layer of peritoneum.
Where does the pancreas sit in relation to the stomach?
Close to the greater curvature of the stomach, with the pancreatic duct extending from the medial end of the gland towards the duodenum.
What is the purpose of bile?
Aids in digestion and absorption of fats and vitamins.
In humans, where is bile stored?
A gall bladder, whose duct joins the bile duct to discharge into the duodenum.
How many lobes does the rat liver have? Do humans have more or fewer?
Four
Fewer
From where does the liver receive venous blood?
From the gut wall via the hepatic portal vein.
From where does the liver receive oxygenated blood?
From the aorta via the hepatic artery, a branch of the coeliac artery.
What system is the spleen a part of?
Lymphatic system
What are the four parts of the large intestine?
Caecum, colon, rectum, anus
What are the purposes of the large intestine?
Reabsorption of water and formation of faeces from undigested food residue.
What contributes to the putrification of the undigested food residue.
Resident bacteria
Describe the caecum
A flabby, thin-walled bag. Human caecum terminates in a vermiform (worm-like) appendix, which contains lymphoid tissue.
Kidneys are said to be retroperitoneal. What is meant by this?
Behind the peritoneum. Ventral surface of each kidney is covered with parietal peritoneum and dorsal surface attached to the body wall.
What is the hilus of the kidneys?
A depression on the medial surface is the the point where the renal artery, renal vein and ureter access the kidney.
What do the outer crust and inner core secrete?
Cortex secretes several steroid hormones whilst medulla secretes adrenaline.
Describe the hard palate.
The anterior roof of the mouth, a bony partition separating the mouth from the nasal cavities above.
Describe the soft palate.
The posterior roof of the mouth, lacking a core of bone.
What is the glottis?
The opening into the trachea.
What is the purpose of the epiglottis?
To prevent food and water entering the trachea during swallowing.
Do rats have a gall bladder?
NO
Which structure of a rat has the most vascular appearance?
Spleen
Why don’t rats have a gall bladder?
Bile is secreted directly into the digestive system by the liver. Rats don’t need bile in large amounts at particular times because they do not have fatty diets.
Describe the reproductive system of female rats.
Y shaped uterus with two arms or horns in which the embryos implant. This shape increases the surface area for implantation, allowing for a larger litter.
What is the only thing found in the peritoneal cavity?
Serous fluid
What is the largest serous membrane?
Peritoneum
What is the peritoneum made up of?
Layers of simple squamous epithelium.
Why is the dissected rat lung different to the normal rat lung?
The rats were killed by using carbon dioxide. This causes haemorrhage from small blood vessels in the lungs. Thus the lungs will be dark red and blood-filled, which is unlike their normal bright pink colour and spongy texture.
What does the pericardial cavity contain?
A supply of serous fluid called the pericardial fluid/
The pyloric sphincter is under __________ ________
Involuntary control
Name the exocrine and endocrine functions of the pancreas.
Exocrine: releases an alkaline digestive juice containing enzymes (lipases, amylases, and proteases) into the duodenum.
Endocrine: secrete hormones (insulin) into the bloodstream.
Describe the appearance of the rat pancreas.
Made of small, scattered, pink lobules suspended by mesentery.
What does the dark red colour of the liver indicate?
Its rich blood supply (vascular) and the fact that its connective tissue capsule is very thin.
What does the soft-jellylike texture of the liver mean it is vulnerable to?
Traumatic injury , which causes severe internal bleeding.
What is the function of the spleen?
Recycling RBC’s
What is the function of the thymus?
Making WBC’s
Where is the spleen found?
On the extreme left side of the abdominal cavity
Describe the appearance of the spleen.
A dark red elongated leaf-shaped organ
How is the spleen similar to the liver?
It lacks a tough capsule and has a generous blood supply.
What is another name for the colon?
Large intestine
Describe the anal sphincter. How is the pyloric sphincter different?
2 bands - 1 voluntary and 1 involuntary
Pyloric has only 1 involuntary band
