Cat Dissection Lab Report

May 26, 2016

Tiffany Zheng, Michelle Wang, Partha Shah

A&P

Cat Dissection Lab Report

System Overviews:

Muscular System (author):

The biceps brachii and the triceps brachii are the two main muscles of the forearm and the fascia is the white tissue that covers all muscles. The biceps brachii are on the other side of the foream, and lie underneath the cat’s shoulder muscle, the clavobrachialis. There are four main muscles of the chest visible in the cat: Pectoantebrachialis (this muscle forms almost a straight line across the top of the chest), Pectoralis major (forms a triangle just under the pectoantebrachialis), Pectoralis minor (a secondary triangle just below the pectoralis major), and the Xiphihumeralis (extends from the armpit of the cat to the center of the chest where the xiphoid process of the sternum rests). The muscle system is used to enable mobility in animals.

Digestive System (author):

The first portion of the small intestine is called the duodenum, which receives secretions from the liver and pancreas.  The last portion of the small intestine is called the ileum, which empties into the large intestine through the ileocecal valve.  The large intestine is also divided into four regions: the colon, cecum, rectum and anal canal.  The first portion of the colon is the ascending colon. The spleen is considered part of the lymphatic system where it participates in producing lymphocytes, filtering blood and destroying old red blood cells.

Cardiovascular (author):

A cat's cardiovascular system (or circulatory system) is the system responsible for circulating blood throughout the body. It consists of the heart and blood vessels, namely arteries, veins and capillaries. The heart is located in the chest between the right and left lungs and is contained in a very thin sac called the pericardial sac. Blood vessels leave the heart and form a conduit system throughout the body that carries blood to all organs, tissues and cells. The right atrium is the collecting chamber for blood from distant parts of the body. Blood is carried back to this upper right chamber of the heart in various veins. The right ventricle is the pumping chamber of the lower right heart. Blood that is high in oxygen returns to the heart from the lungs and enters the upper left chamber of the heart, the left atrium.

Endocrine (author):

A cat's endocrine system is composed of several different types of glands and organs that produce the hormones of the body. There are two adrenal glands located in the abdominal cavity directly in front of the kidneys. The pancreas is located in the forward part of the abdominal cavity, behind the liver and stomach. The endocrine glands produce hormones, and secrete them directly into the internal environment where they are transmitted via the bloodstream. Hormones produce certain effects at different points in the body. Some endocrine glands are directly under the control of the pituitary gland. For example, the adrenal gland is controlled by the pituitary hormone, adrenocorticotropic hormone (ACTH). ACTH causes the adrenal glands to produce cortisone (cortisol), which is also a hormone.

Respiratory (author):

The respiratory system is basically composed of the nares (nostrils), nasal cavity, sinuses within the skull, pharynx (back of the mouth), larynx (voice box), trachea (windpipe), bronchi (the branches of the trachea going into the lungs), and the lungs. The cat's respiratory system serves two purposes. First, it is the exchange mechanism by which the body's carbon dioxide is replaced with oxygen. It is also a unique cooling system. The diaphragm muscle separates the chest, containing the heart and lungs, from the abdomen which holds the intestines, stomach, liver, bladder, etc. The trachea carries the air to the bronchi, which in turn supply the lungs.

Reproductive (author):

The female genital tract consists of the vulva, vagina, cervix, uterus, oviducts, and ovaries, as well as the mammary glands found on the chest and abdomen. Ovaries are female gonads that produce eggs and female sexual hormones, including estrogen and progesterone. Estrogen is necessary for the development of eggs, and progesterone prepares the uterus for pregnancy. The oviducts are small tubes that connect the ovaries to the uterus. The end of the uterus is called the cervix. It separates the uterus from the vagina and provides a barrier against infection. The vagina, a muscular tube that extends from the cervix to the outside, is connected to the vulva, which is the external opening of the female genitals.

Dissection Checklist:

Pectoralis major	Near the chest Gives movement to shoulder
Pectoralis minor	Between the chest and armpit Depresses the shoulder
xiphihumeralis	Muscle that extends to xiphoid cartilage Move humerus bone
Rectus Abdominis	Two parallel muscles in the abdominal region Flexing the spine
Clavotrapezius	Anterior trapezius muscle Clavicle dorsally goes toward the head
acromiotrapezius	Middle trapezius muscle Scapula to dorsal together
spinotrapezius	Posterior trapezius muscle Scapula to dorsal
clavobrachialis
acromiodeltoid
Latissimus Dorsi	Dorsal vertebrae Moves back
Splenius	Two muscles attached to vertebrae Moves neck
Supraspinatus
Infraspinatus
Triceps brachii
Tensor Fasciae Latae
Gluteus medius
Biceps Femoris
semitendinosus
Sartorius
Gracilis
Thyroid gland
Thymus
pancreas
Aortic arch
Right and left common carotid arteries
Renal arteries
Inferior vena cava
Renal veins
External nares
larynx
Spleen
diaphragm
Esophagus
liver
Gallbladder
stomach
pancreas
duodenum
Large intestine
Ascending colon
Transverse colon
Descending colon
rectum
Urinary Bladder
uterus
Testes
Ovaries
Uterine Tubes
Vena cava
Rectum
urethra
Left uterer
ileum
cecum
Ascending aorta
Submandibular gland
brachialis
Sartorius
peritoneum
adductors

Reflexes Lab Analysis

1. Give a recap of what you did in this lab. Relate what you learned about neurons and reflexes in lecture to the applications in this lab. For example, what is a reflex, and how does it work?

In this lab, we tested different reflexes including the photopupillary reflex, knee jerk reflex, blink reflex, plantar reflex, and reaction time. Reflex actions are involuntary—they happen before you have time to think. When they happen, a nerve signal takes a shortcut through the spinal cord, rather than involving the brain. If we touch a very hot object, a sensory neuron sends a signal shooting from the hand to the spinal cord.

1. Claims Evidence Reasoning: For each of the 5 parts, write a claim that explains what the specific reflex is.   Cite your evidence of it happening, or not, and then provide your reasoning for why that particular reflex occurred. If it didn’t, why?

In the photopupillary reflex part, a person covers his or her eyes with hands for an extended period of time and then is shined in the eye with a bright flashlight. The iris became a lot smaller, as the amount of light entering the eye triggered the reflex. The pupil contracts so that less light enters the eye.

In the knee jerk reflex/ patellar reflex portion, the spot just below my knee cap was hit with a small hammer, resulting in my leg immediately kicking out. This reflex, called a monosynaptic reflex, occurs because the knee tap causes the thigh muscle to stretch. This simultaneously sends out information to the spinal cord. When the quadriceps are fatigued, the patella reflex does not occur.

The blink reflex was tested when a clear sheet was held over my face and a cotton ball was thrown at it. Even though I understood that there was a barrier between the cotton ball and my face, I still blinked. This reflex occurred because humans instinctually will close their eyes if something is heading towards their eyes.

The plantar reflex was tested when a pen was dragged up the bottom of a foot. Naturally, the toes flexed and came closer together. This reflex occurred because the nerve system in developed humans is fully myelinated.

Lastly, we tested reaction time by dropping a ruler and measuring how far down it took for the person to close their hand and catch the ruler. I noticed that with each trial, the trial distances decreased as we got used to catching the ruler. However, when we texted, the first trial distance was more than twice the distance of the first regular trial distance. The first trial was 23 cm while the first trial with texting involved was 50 cm. However both trials decreased in distance for the next two trials.

Brain Dissection Lab Report

In class today, we performed a dissection and identification process on a sheep brain. We began by using the forceps to remove the meninges, or the 3 layers of tissue that protect the brain and spinal cord, to see all the different sections of the brain more clearly. We then cut the brain longitudinally to observe the medial plane of the brain. Lastly, we used the scalpel to make a cross sectional cut of the cerebrum to expose the grey and white matter. The different areas of the brain are identified and labeled with pins and sketches.

The cerebrum, labelled with the yellow pin, is responsible for higher brain function like thought and action. The cerebellum, marked with the green pin, receives information from the sensory system and regulates motor movement. The brainstem, marked with the red pin, regulates heart rate, breathing, sleeping, and eating. The anterior part of the brain is marked with the white pin while the posterior portion is marked with black. 

A myelin layer increases the speed at which impulses propagate along the myelinated fiber. 

The thalamus, marked with the yellow pin, relays and processes sensory and motor information.

The optic nerve, marked with the green pin, transfers visual info from retina to the brain via electrical impulses.The medulla oblongata, marked with the red pin, relays sensory info to the thalamus and regulates visceral functions like cardio, respiration, and digestion. The pons, which has a blank pin, relays sensory information to the cerebellum and thalamus and acts as a subconscious somatic and visceral motor center. The midbrain, which has a blue pin, is associated with vision, hearing, motor control, alertness, and temperature regulation. The corpus callosum, marked with a white pin, integrates functions between the cerebral cortex on one side of the brain to the same region on the other side. The hypothalamus, marked with a black pin, is a center for controlling emotions, autonomic functions, and hormone production.

Grey matter is the darker tissue of the brain and spinal cord, consisting of mainly nerve cell bodies and branching dendrites. White matter is composed of bundles of myelinated nerve cell processes or axons which connect areas of grey matter and carry nerve impulses between neurons. Myelinated means that the axon is covered by the myelin sheath, thus increasing the speed of the impulse. Unmyelinated means that the axon is not covered by the myelin sheath, thus reducing the speed of the impulse. 

Sheep Eye Dissection Lab

From the anterior view of the sheep eye, the eyelid, cornea, sclera, and fatty tissue are visible. The posterior view of the eye presents the optic nerve, the extrinsic muscle, and more fatty tissue, which covers the entire outer area of the eye. In the internal posterior view, the vitreous humor, retina, and choroid can be observed. The internal anterior view shows the ciliary body, lens, pupil, and iris.

The sclera is the tough and thick white outer cover of the eyeball. It is covered with a layer of fatty tissue and muscle tissue. The choroid brings blood, oxygen, and nourishment to the eye. The cornea, which is the cloudy and tough cover over the iris and is located just behind the the pupil's opening, helps to protect the eye and focus light. The cornea is cloudy due to the cataract condition, which prevents or reduces the amount of light that reaches the cornea. The iris, which is the brown colored part of the eye controls the amount of light that penetrates the eye. The lens, which is the clear structure that adjust the eye's focus and is responsible for about 20% of the eye's focusing, was surrounded by the ciliary body. The ciliary body encircles the lens and controls its shape with muscles.





The optic nerve is a bundle of nerve fibers that carry information from the retina to the brain for processing. The pupil is the oval shaped hole that allows light to enter the eye. In humans, the pupil is circular. The retina is the layer of light sensitive cells that line the inner eyeball. The retina contains rods, which are photoreceptor cells that respond to dim light. The vitreous humor is the clear gel that fills the space between the lens and the retina of the eyeball.




The tapetum lucidum, which reflets light back into the retina, is the iridescent blue, shiny, and reflective material located directly behind the retina and is part of the choroid layer in nocturnal animals. Although humans lack the tapetum, animals use this to see in the dark, which is why animal eyes glow occasionally glow in pictures with flash.

Relate & Review: The Woman With a Hole In Her Brain

The woman in the article was missing her cerebellum, which is responsible for motor memory and body control. The cortex took over the responsibilities of the cerebellum and she was able to survive with only a few issues. Another part of the brain, the pons, is the portion that lies above the medulla oblongata and below the midbrain. It transmits sensory info and motor impulses from the brain. It also controls the subconscious somatic and visceral motor centers. An injury to the pons can result in coma, sleep or sensory disturbances, and increase levels of anxiety and stress. A severe injury or absence of the pons would result in death, so a person cannot live without his or her pons.

The Clay Brain

In class today, we created brain models out of clay to showcase the different components of the brain. One model was of the left hemisphere from the right looking at the sagittal plane. The second was a lateral view of the right cerebral hemisphere. each part is differentiated with different colors of clay.

Unit 7 Reflection: Muscles

Our muscle video:

Muscles are composed of actin and myosin fibers and are classified into three groups: skeletal, cardiac, and smooth. Muscles have four properties: excitability, contractility, extensibility, and elasticity. Contractility is the ability for muscle tissue to shorten when stimulated. Extensibility is the opposite or the ability for muscles tissues to be stretched. Elasticity is the muscle tissue's ability to recoil back to resting length. Connective tissue components include the fascia, which hold muscle fibers together. The perimysium separates muscles into bundles. Tendons connect muscle to bone.

Muscles have many roles and vary in size and function. Masseter elevates the mandible and the temporalis elevates and retracts the mandible. The trapezius extends the hand and can adduct, elevate, or depress the scapula. The latissimus dorsi can extend, adduct and rotate the arm medially. The biceps brachii can flex the elbow joint while the triceps brachii can extend the elbow joint. The Brachioadiatis flexes the forearm at the elbow and is responsible for supination and pronation. The rectus abdominus can flex the abdomen while the external oblique can compress the abdomen. External intercostals elevate ribs while internal intercostals depress ribs. The hamstring group includes the biceps femoris, which flexes the lower leg, the semimembranosus, the most medial of hamstring muscles and extends the thigh, and the semitendonosus, which is anterior and medial to the semimembranosus on the inside of the thigh. Quadriceps muscles include the rectus femoris, vastus intermedius, vastus medialis, and the vastus lateralis.


Slow twitch fibers, or slow oxidative, are relatively slow and are aerobic. They have a low number of glycogen stores and are red in color, as they have a lot of oxygen. They are best suited for long distances and have high amounts of myoglobin, mitochondria, and capillaries. Fast twitch a fibers are relatively fatigue resistant while fast twitch b fibers fatigue quickly. FTa fibers are red to pink in color while FTb fibers are white or pale in color. An example of a concentric contraction is a bicep curl and an example of an isometric contraction is holding a weight out in front of you. An example of an eccentric contraction is walking. The ratio of muscle fibers varies between individuals and depends on genetics and exercise. Active exercise can result in hypertrophy (cells increase in size/volume due to an increase in myofibrils) and hyperplasia (cells remain the same size but increase in number).

Performance enhancing substances are manufactured products for oral ingestion, intranasal application or inhalation containing compounds that are intended to increase performance, promote muscle growth or induce weight loss. Health risks for men include shrinking of testicles, low sperm count, impotence, breast growth, and an enlarged prostate. Health risks for females include breast shrinkage, facial hair growth, issues with menstrual periods, and an enlarged clitoris. However, not all performance enhancements are bad for you (read more in my last blog post).

Because college decisions are coming out and I have been more busy, I haven't been able to keep up with my New Years resolutions as much as I'd like. My first goal of sleeping more has not been working out as well as I had hoped, but I want to start setting a timer whenever I do work to maximize efficiency. This will help me accomplish my second goal of studying anatomy notes every night as well. If I manage my time by setting a personal deadline, I know I will be able to catch up to what I originally had hoped.