Gross Anatomy - Anatomy

The atrium and ventricle on each side of the heart are separated from one another by the atrioventricular valves. There is also another pair of valves that separate the ventricles from the arteries exiting the ventricles, known as the semilunar valves. The semilunar valves are the pulmonary and aortic valves, which separate the ventricles from the pulmonary trunk and aorta respectively. The tricuspid valve is found between the right atrium and ventricle, while the mitral (bicuspid) valve is found between the left atrium and ventricle.

T-lymphocytes mature in the thymus, where they interact with "self antigens." This process ensures that T-lymphocytes do not interact with antigens found in the body. If the immature cell interacts with self antigens, the T-lymphocyte will be destroyed. Mature T-lymphocytes that still react to self antigens can cause allergic reactions and autoimmune disease.

B-lymphocytes, in contrast, mature in the bone marrow. Both types of lymphocyte originate from stem cells in the bone marrow, but differ in their site of maturation.

B-lymphocytes mature in the bone marrow. They can also be created and matured in the liver. Both types of lymphocyte originate from stem cells in the bone marrow, but differ in their site of maturation.

T-lymphocytes mature in the thymus, where they interact with "self antigens." This process ensures that T-lymphocytes do not interact with antigens found in the body. If the immature cell interacts with self antigens, the T-lymphocyte will be destroyed. Mature T-lymphocytes that still react to self antigens can cause allergic reactions and autoimmune disease.

Mature lymphocytes are most commonly found in the lymph nodes, where they screen the plasma and fluids for antigens.

The skin is made up of two major components: the superficial epidermis layer and the deep dermis layer. The epidermis is essentially made up of four layers, however, there is an additional layer found in regions of thick skin. The four principle epidermal layers, going from superficial to deep, are the stratum corneum, stratum granulosum, stratum spinosum, and stratum basale. In regions of thick skin (namely the soles of the feet and palms of the hands) there is an additional layer of cells located between the stratum corneum and stratum granulosum, known as the stratum lucidum, which serves to enhance protection and cushioning of these areas.

There are two types of sweat glands: eccrine and apocrine. Apocrine sweat glands are slightly larger and open into hair follicles. They produce an odorous, thicker fluid in comparison to eccrine glands. Apocrine glands are located at the perianal, axillary, and areolar regions on the body, as well as the ear canal and eyelids. The ear canals and eyelids house modified apocrine sweat glands that produce specialized secretions.

Eccrine sweat glands are located basically everywhere and open onto the skin surface. The fluid produced is more viscous, containing water, sodium chloride, urea, ammonia, and uric acid.

A hair has two principle parts: the shaft and the root. The shaft is seen above the skin and the root stays deep within the skin surface. The shaft and the root are made of keratinized epithelial cells, which have ceased to divide and are considered non-living. The cells of the hair are organized into three layers. The cuticle is the outermost layer, which wraps around the hair exterior. The next layer is the cortex, which surrounds the innermost layer, the medulla. The root sheath structure is separate from the actual hair and is constructed from living epithelial cells that anchor and nourish the hair.

The four leg compartments are anterior, lateral, superficial posterior, and deep posterior.

The anterior compartment contains muscles, nerves, and vessels for dorsiflexion. From medial to lateral, these are the: tibialis anterior, extensor hallucis longus, anterior tibial artery, deep peroneal nerve, extensor digitorum longus, and peroneus tertius. The lateral compartment consists of the peroneus longus and brevis, and superficial peroneal nerve for feet eversion. The superficial posterior compartment is for plantarflexion, consisting of the gastrocnemius and soleus muscles and the sural nerve. The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, posterior tibial artery and vein, tibial nerve, and flexor hallucis longus.

All of these compartments need to be evaluated when a tibia fracture occurs, as pressures could rise and cut off nerve and/or vascular supply.

The heart is the pump that distributes oxygenated blood throughout the body and is enclosed in a sac known as the pericardium. The pericardial sac is made of the fibrous and serous pericardium. The heart has four chambers, which are divided by septums to prevent exchange of blood between adjacent chambers. The chambers of the heart are the right atrium, right ventricle, left artium, and left ventricle. The right atrium receives blood from the superior and inferior vena cavae. Blood then passes from the right atrium to the reight ventrical via the tricuspid valve. The right ventricle pumps blood into the pulmonary arteries for transport tot he lungs to receive oxygen. Following gas exchange, the pulmonary veins return the blood to the left atrium of the heart. The blood them passes through the bicuspid (mitral) valve before entering the left ventricle. The left ventricle pumps the blood into the aorta to be carried through arteries to the tissues of the body.

The middle mediastinum is the area bordered by the left and right pleural cavities. The major structures found within the middle division are the heart, the pericardium, the main bronchus, phrenic nerves, arch of the azygos vein, and the vessels coming out of the heart such as the aorta, pulmonary arteries, and veins. The arch of the aorta and the trachea are found in the superior mediastinum. The esophagus is found in the superior and posterior mediastinum.

The musculocutaneous nerve arises from the lateral cord of the brachial plexus. It innervates the biceps brachii, the coracobrachialis, and the brachialis muscle. All of these are muscles of the anterior arm.

The crista terminalis is a specialized region in the upper part of the right atrium. It houses the sinoatrial (SA) node, which is responsible for initiating the electrical impulses that cause the heart to contract.

The tricuspid valve separates the right atrium and the right ventricle. The bicuspid, or mitral, valve is located between the left atrium and left ventricle. The pulmonary valve is a semilunar valve that prevents backflow of blood from the pulmonary veins into the right ventricle.

There are five muscles in the anterolateral group of abdominal muscles (three flat muscles and two vertical muscles). The three flat muscles include the internal and external oblique and the transversus abdominis. The two vertical muscles include the rectus abdominis and pyramidalis muscles.

The trapezius muscle is one of the superficial, upper back that originates in the spinous processes of C1-C7. Of the possible nerves, only the accessory nerve innervates muscles in the upper, superficial back. The trapezius is one of two muscles that is innervated by the accessory nerve, the other being the sternocleidomastoid.

In order for a muscle to depress and lower the thyroid cartilage, it needs to originate below and insert either at or above the thyroid cartilage. The correct answer is the sternothyroid. This muscle originates at the sternum and inserts at the thyroid cartilage. When this muscle contracts, the action causes the thyroid/larynx to lower and depress.

For this question, we are looking for a muscle that is located around the eye and thus responsible for its movement. The correct answer is the orbicularis oculi which is the only muscle of the answer choices that fits. Although each of these muscles is located in the face, none of the other choices are around the eye.

The superior oblique muscle in the upper/middle part of the eye. That means that when this muscle contracts, the eye will be pulled towards the center of the face. In anatomical position, this action is described as a medial, or towards the midline, rotation.

We are looking for a muscle around the mouth, leaving us with the risorius, orbicularis oculi, and zygomaticus minor muscles. The orbicularis oculi protrudes the lips and the zygomaticus minor elevates the upper lip. This means that the correct answer is the risorius muscle.

Of the answer choices, the risorius and master muscles control movements around the mouth and jaw. The orbicularis oculi is responsible for movement of the eyelid. This means that the correct answer is the procerus muscle.