Humans Vs. Rats

Homo sapiens and Rattus norvegicus– Comparative Discussion

Digestive System

The overall digestive tract is very similar anatomically in rats and humans. The major difference is that rats lack a gall bladder. Instead, their bile, bodily fluid that breaks down lipids, flows directly from the liver to the small intestines. Rats also lack the ability to regurgitate due to the build of their esophagus and stomachs. The rat digestive tract is noticeably shorter than the human digestive tract. Rats do not have an appendix at the end of the caecum like humans do.

Respiratory System

The general structure of the Respiratory System in Homo sapiens and Rattus norvegicus is similar. The rat’s respiratory system is significantly smaller in size. Both humans and rats inhale oxygen and exhale carbon dioxide, like other animals. A two-part respiratory system, upper and lower, exists in both. However, in humans, the right lung has three lobes, and the left lung has two lobes. In rats, the left lung has two lobes, and the right lung has four lobes. Rats also able to take more breaths in a minute.

Circulatory System

Both Homo sapiens and Rattus norvegicus circulate their blood through a closed Circulatory System called the cardiovascular system. Both have a four-chambered heart, seeing as they are both mammals. Both use blood to transport nutrients, wastes, water, oxygen, and carbon dioxide throughout the body. The rat’s circulatory system is smaller in size. Rat has a caudal artery that brings blood to the tail. This is absent in humans.

Urinary System

The urinary system within humans and rats is very similar in structure and function. It is responsible for processing the waste products of metabolism. The major organs and parts that make up the urinary system in both humans and rats include the kidneys, ureter, urinary bladder, and urethra. Also, humans and rats are two examples of how waste removal is a crucial part in maintaining homeostasis. In humans and rats, the first thing that happens in the urinary system is blood enters the kidneys through the renal artery and exits through the renal vein. As the blood passes through the kidneys, millions of nephrons or excretory tubules within the kidneys filter out blood plasma, nitrogenous wastes, urea, salts, ions, glucose, and amino acids. Then the nephrons reabsorb the substances needed by the body from the filtrate and return them to the blood. Then the waste fluid, urine, leaves the kidneys through the ureter which drains into the urinary bladder where it is temporarily stored. From there, the urine passes through a tube called the urethra and exits the body during urination. The urinary system of a rat and a human is almost identical. The only major difference is the size of the organs between that of a human and that of a rat.

Reproductive System

Female

In female humans and rats, the main organs that compose their reproductive system consist of the ovaries, oviducts, uterus, and vagina. A difference between female rats and humans is that a rat’s vagina connects to the urogenital aperture and humans do not have a urogenital aperture. The vagina is a short, muscular canal located below the urethra. Also, the rat’s vagina is much shorter in length than the human vagina. In female rats, the ovaries which produce egg cells (ova) and female hormones (estrogen and progesterone), are small and located just below the kidneys inside the peritoneal membrane. Also, the shape of the uterus in rats is different than in humans. In rats it is Y-shaped and in humans it’s a pear shaped organ. Furthermore, rats do not undergo menstruation such as humans do. Instead, in rats, ovulation is provoked by mating.

Male

In male humans and rats, the major organs that make up their reproductive system include the testes, scrotum, epididymis, prostate glands, seminiferous tubules, vas deferens, seminal vesicles, urethra, and the penis. In both humans and rats, the testes located in the scrotum, are the reproductive organs that produce sperm and male hormones (testosterone). The seminiferous tubules which are tightly packed coils located in the testes are the place in which sperm develop. In rats and humans, sperm are stored in the epididymis which is adjacent to the testes. Also, rats and humans both produce seminal fluid inside the prostate gland and seminal vesicles. A difference between rats and humans is that rats have a urogenital aperture and humans do not. Another major difference between rat and human male reproductive systems is that, during the non-breeding periods, rats possess the ability to retract the testes into the abdominal cavity. Humans cannot do this.

Works Cited

BSCS Biology: A Molecular Approach. Columbus, OH: Glencoe/McGraw-Hill Publishing Company, 2006. Print.

Bohensky, Fred. Photo Manual and Dissection Guide of the Rat. USA: Square One Education Guides, 2002. Print.

Kimball, John. Kimball’s Biology Pages. 2010. Web. 2 June 2010.

National Kidney and Urological Diseases Information Clearinghouse. n.d. Web. 2 June 2010.

Rat Breeding Giode. n.d. Web. 2 June 2010.

WebMD. 2005. Web. 2 June 2010.

Damon, Alan. Biology: Higher Level (plus Standard Level Options) : Developed Specifically for the Ib Diploma . Harlow: Heinemann, 2008. Print.