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October, 2006
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Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (Epithelium) or masses. Epithelial cells lining the Skin; the Mouth; the Nose; and the Anal canal derive from ectoderm; those lining the Respiratory system and the Digestive system derive from endoderm; others (Cardiovascular system and Lymphatic system) from mesoderm.


JoVE 10696

Cells with similar structure and function are grouped into tissues. A group of tissues with a specialized function is called an organ. There are four main types of tissue in vertebrates: epithelial, connective, muscle, and nervous.

Epithelial tissue consists of thin sheets of cells and includes the skin and the linings of internal organs and body cavities. Epithelial cells are tightly packed, providing a barrier against injury, infection, and water loss. Epithelial tissue can be a single layer called simple epithelium, or multiple layers called stratified epithelium. In stratified epithelium, such as the skin, the outer cells—which are subject to damage—are replaced through the division of cells underneath. Epithelial cells have a variety of shapes, including squamous (flattened), cuboid, and columnar. Some epithelial tissues absorb or secrete substances, such as the lining of the intestines. Connective tissue is composed of cells within an extracellular matrix and includes loose connective tissue, fibrous connective tissue, adipose (fat) tissue, cartilage, bone, and blood. Although the characteristics of connective tissue vary greatly, their general function is to support and attach multiple tissues. For example, tendons are made of fibrous connective tissue and attach muscle to bone. Blood transports oxygen, nutrients and waste produ

 Core: Biology

What is Monogastric Digestion?

JoVE 10829

The human body contains a monogastric digestive system. In a monogastric digestive system, the stomach only contains one chamber in which it digests food. Several other animal species also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter, however, focuses on the human digestive system.

Saliva is a watery substance secreted by the salivary glands into the mouth. Human saliva contains 99.5% water with electrolytes, mucus, white blood cells, epithelial cells, enzymes, and antimicrobial agents. The enzymes found in saliva are essential in beginning the process of digestion. They also play a role in breaking down food particles trapped around the teeth, protecting them from decay. Saliva is obtained easily, inexpensively, and non-invasively from patients which spurs research interest. Ongoing research identified novel ways of using saliva in molecular diagnostics. DNA, RNA, and proteins found in saliva serve as useful sources of diagnostic information in the early detection of various cancers including oral, pancreatic, and gastric cancer. The primary component of gastric acid is hydrochloric acid. Hydrogen and chloride ions released by parietal cells lining the stomach react in the stomach cavity to form hydrochloric acid. Parietal cells are coupled to feedback systems that increase and decrease acid prod

 Core: Biology

DNA Isolation and Restriction Enzyme Analysis- Concept

JoVE 10628

The revelation of DNA as the hereditary molecule in all organisms has led to enormous scientific and medical breakthroughs and significantly enhanced our understanding of ourselves and other organisms. DNA isolation and profiling have been the fundamental first steps for many of the advancements in the past century; from identification of gene function, to revolutions of agriculture and…

 Lab Bio

Osmoregulation in Insects

JoVE 10990

Malpighian tubules are specialized structures found in the digestive systems of many arthropods, including most insects, that handle excretion and osmoregulation. The tubules are typically arranged in pairs and have a convoluted structure that increases their surface area.

Malpighian tubules extend from the digestive tract, typically the area between the midgut and hindgut, into the hemolymph—a mixture of blood and interstitial fluid found in insects and other arthropods, as well as most mollusks. Unlike other excretory systems, the excretory processes of Malpighian tubules lack a filtration step. Metabolic wastes, like uric acid, diffuse into the tubules from the hemolymph. The tubules are lined with a layer of transport epithelia. These specialized epithelial cells contain pumps that actively transport ions, like sodium (Na+) and potassium (K+), from the hemolymph into the interior of the tubule, called the lumen. Osmosis allows water to follow ions into the tubules passively. From the tubule lumen, water, ions, and waste travel from the intestine to the rectum. Tiny, protruding microvilli lining the inside of the tubules help maximize solute-water coupling and the propulsion of uric acid crystals through the tubules. In the rectum, specialized glands pump many of the ions back into the hemolymph. Osmo

 Core: Biology

Anatomy of the Intestines

JoVE 10830

Although digestion of proteins, carbohydrates, and lipids may begin in the stomach, it is completed in the intestine. The absorption of nutrients, water, and electrolytes from food and drink also occur in the intestine. The intestines can be divided into two structurally distinct organs—the small and large intestines.

The small intestine is an ~22 meter-long tube with an inner diameter of just 2.5 cm. Since most nutrients are absorbed here, the inner lining of the small intestine is highly convoluted and covered in finger-like extensions called villi, each containing hundreds of microvilli. The folds, villi, and microvilli of the small intestine amplify the surface area of absorption 60 to 120 times. The increased surface area provides ample opportunity for nutrients to be absorbed. The small intestine connects to the stomach by the pyloric sphincter, which closes off when chyme moves into the duodenum—the beginning of the small intestine. The middle and largest part of the small intestine is the jejunum. The ileum ends the small intestine, where it attaches to the large intestine by the ileocecal valve. The large intestine starts at the cecum. The appendix, a small lymphatic structure, dangles from the bottom of the cecum. Above the cecum, starts the ascending colon followed by the transverse colon. They absorb most of the remaining

 Core: Biology
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