Tissues, Organs, and Organ Systems - Biology

Adipose tissue is one of the main types of connective tissue. It is also known as fat, and is a loose connective tissue composed mostly of adipocytes.

All of these areas of the body are subject to lots of friction. Thus, there would be multiple (stratified) layers of epithelium lining them.

Relay of electrical signals is performed by the nervous system, not by connective tissue.

Filtration occurs in the renal corpuscle, which is composed of the glomerulus and Bowman's capsule. The glomerulus filters the blood, resulting in the filtrate, which will then go through the tubules. The proximal and distal convoluted tubules are primarily involved in solute reabsorption, and the loop of Henle helps concentrate the urine.

Cartilage is a flexible connective tissue found throughout the body in places such as the ear, nose, bronchial tubes, and intervertebral discs. It is not as hard as bone, but it is stiffer and less flexible than muscle. Cartilage is composed of specialized cells named chondrocytes. These cells produce and maintain the cartilaginous matrix, which is composed of collagen and proteoglycan.

Insulin stimulates the reuptake of glucose from the blood into the cells. Thus, the glucose levels in the blood decrease, as the glucose is taken into cells. The cells may either store it as glycogen (in liver and skeletal muscle) or use it in glycolysis to make ATP.

The pituitary gland is known as the "master" endocrine gland because it secretes several hormones that control other endocrine glands. These are known as tropic hormones. Adrenocorticotropic hormone, thyroid-stimulating hormone, and follicle-stimulating hormone are some examples of pituitary tropic hormones.

Steroid hormones are the only ones derived from cholesterol and are always characterized by a four ring molecular structure. Some examples include sex hormones such as androgens and estrogens as well as some adrenal hormones like cortisol (a glucocorticoid) and aldosterone (a mineralocorticoid).

Increased potassium levels will stimulate aldosterone to increase potassium secretion. The main regulators of aldosterone are potassium and the renin-angiotensin pathway.

Osteogenic cells are a type of stem cell that differentiate into osteoblasts, which allow bone to form. Eventually, osteoblasts will become enveloped into the bone matrix and differentiate into osteocytes. Osteoclasts have the opposite function of osteoblasts, and are responsible for the resorption of bone matrix. This releases calcium into the bloodstream by breaking down bone.

Red bone marrow is found in the epiphyses, or ends of long bones. It is the site of hematopoiesis, or red blood cell development.

Yellow bone marrow is primarily composed of fat. Osteons are the functional units of bone, and house the cells that build and break down the bony matrix. Cartilage is found on the articular surfaces of bone, and helps provide support for joints.

The skeletal system has a variety of functions, including protecting internal organs, storing minerals and energy molecules, and assisting in movement.

The production of heat, however, is a function of the muscular system.

Progesterone ("pro-gestation") is responsible for the maintenance of a pregnancy. Initially, the corpus luteum secretes progesterone in preparation for pregnancy. Then, after fertilization, human chorionic gonadotropin (hCG) is released which causes the corpus luteum to keep secreting progesterone. The placenta takes over it's function after 6 weeks gestation.

Eggs, or oocytes, are produced in the ovaries. During ovulation, the egg is released from the ovary into the fallopian tube. If fertilized, the egg transitions into a zygote and is implanted into the uterus for gestation and development.

The spleen is involved in filtering the blood and lymph, and is not involved in reproduction.

The epididymis is responsible for storing sperm in order for it to mature. Upon ejaculation, it will be propelled into the vas deferens and out of the urethral opening.

Connective tissue is responsible for binding organs together and is defined by a set of common cells suspended in an extracellular matrix. Blood, bone, adipose, and ligaments are all considered connective tissue.

Epithelial tissue covers body surfaces, nervous tissue detects changes in the environment, and muscular tissue generates force by contracting.

Connective tissue has a wide variety of functions, including all of the given answer options. Along with epithelial tissue, connective tissue is one of the more versitile tissues in the body. Bone, cartilage, and fibrous connective tissue provide support and protection to organs. Loose connective tissue and fibrous connective tissue are common components of basement membranes and connective structures that bind organs together; ligaments and tendons perform similar functions for muscle and bone connections. Adipose tissue (fat) is used to store energy for long periods.

The endothelium is a form of squamous epithelium consisting of flat cells that line the blood and lymphatic vessels. Endothelial cells are metabolically active and produce compounds that relax vascular smooth muscle and inhibit the adhesion of platelets.

Adipose, or fat cells, are modified for long-term energy storage and are considered connective tissue. Cone cells are found in the eye and serve as light receptors for the nervous system. Stem cells can develop into more specifically differentiated daughter cells. Dendritic cells help T-cells respond to foreign antigens as part of the immune system.

An epithelia is a sheet of cells that are closely associated. Cells within an epithelium are polarized, indicating that the cells have a "direction". One side of the epithelium is called "apical" while the other side is "basal." The apical region is oriented toward a lumen, while the basal region is oriented toward a basement membrane associated with connective tissue. Cells within an epithelium are innervated, but not vascularized; therefore, they must receive signals through other methods of intercellular signaling, such as tight junctions.

The epidermis is composed of five layers of flattened epithelial cells. This stratified squamous epithelium allows the skin to be a barrier for the body and prevent pathogens and foreign materials from entering.

Stratified epithelium has multiple layers, and squamous epithelium is flattened.