• In common parlance, a body system is understood to be a collection of organs and other body elements that work together to accomplish one primary function.

• The systems are connected to one another and are depending on one another, but each has its own distinguishable parts.

• The organs and tissues that make up a system are the primary components of that system.

• The majority of organs are made up of a variety of tissues.

• For example, the neurological system, connective tissue, and epithelium (covering or lining) cells can all be found in the brain.

• A group of cells that have the same structure and function is called a tissue.

• Tissues are made up of groups of cells.

SYSTEM

• One of the body's systems that is particularly well understood is the digestive system.

• It is made up of a long tube known as the digestive tract as well as glands that are related with it.

• These organs include the liver and the pancreas, both of which dump their products, such as enzymes, into the main tract through ducts that connect them to the main tract.

ORGAN

• The liver is the body's largest internal organ, weighing an average of 31/3 pounds (1.5 kilograms) in adults.

• This is slightly more than the weight of the brain.

• The liver contains a network of tubes that are responsible for transporting the liver's waste product, bile, to the gallbladder, which is a tiny sac located directly under the liver's right end.

ORGAN SUBSTRUCTURE

• Hepatocellular lobules are the structural-functional units that make up the liver.

• The lobules each have six sides, and both within the lobules and between them are blood arteries and bile ducts.

Kupffer cell

• This type of white blood cell is exclusive to the liver and is also known as a hepatic macrophage.

• It is responsible for consuming and digesting old, worn-out blood cells as well as other waste.

TISSUE

• The distinctive structure of the liver's connective tissue is made up of laminae, which are sheets of liver cells (hepatocytes) arranged in an angled pattern.

• These are filled with fluids and contain microscopic branches of the two most important kinds of tubes, which are blood arteries and bile ducts.

CELL

• A typical cell is able to obtain its own source of energy and to process the nutrients that it takes in.

• Cells serve as the fundamental living unit of all tissues in the body.

• Hepatocytes are a type of cell that may be found in the liver.

• These cells are examples of body cells and contain a wide variety of organelles, which are very small structures.

Bile canaliculus

• The bile duct's most smallest branch, which winds its way through the hepatocytes.

Sinusoid

• A blood vessel that has numerous pores that enable the blood to exchange oxygen and nutrients with the surrounding tissue.

Bile duct

• Drains the bile fluid, which is produced by the hepatocytes, into the canaliculi.

Microvilli

• Some cells have projections, which serve to enhance the total surface area of the cell.

Centriole

• Two cylinders made up of tubules, both of which are necessary for reproduction.

Microtubule

• Constitutes a component of the cytoskeleton and contributes to the movement of constituents within the cytoplasm.

Mitochondrion

• The location in the cell where digestion of sugar and fat takes place; the source of cellular energy

Vacuole

• A sac that collects and carries water, waste, and the materials that have been ingested.

Nucleolus

• Located in the middle of the nucleus, this area is important in the creation of ribosomes.

Nucleus

• The command and control hub of the cell; contains chromatin and the vast majority of the cell's DNA

Nuclear membrane

• A membrane consisting of two layers, each of which contains pores through which substances can travel.

Nucleoplasm

• The fluid that is contained within the nucleus.

Cytoskeleton

• Microfilaments and microtubules make up the cytoskeleton, which is the internal framework of the cell.

Microfilament

• Provides support for the cell

Cytoplasm

• Jellylike fluid that contains organelles

Released secretions

• Exocytosis is the process by which secretions are discharged; a vesicle fuses with the cell membrane and then releases its contents.

Secretory vesicle

• a sac that is secreted at the cell membrane that includes a variety of compounds that are produced by the cell, such as enzymes.

Golgi complex

• This organelle is responsible for the processing and repackaging of proteins that have been generated in the rough endoplasmic reticulum in preparation for their release at the cell membrane.

Lysosome

• Produces enzymes that assist in the digestion of various substances as well as worn-out organelles

Peroxisome

• Makes enzymes that oxidize some toxic chemicals

Smooth endoplasmic reticulum

• A network of tubes and flat, curving sacs that assist in the transfer of materials throughout the cell; the site of calcium storage; the primary metabolic center of the cell

Rough endoplasmic reticulum

• Folded membranes that are dotted with ribosomes; aid in the movement of materials throughout the cell; the primary location of protein synthesis

Cell membrane

• encloses the contents of the cell and regulates the movement of chemicals into and out of the cell

Ribosome

• Involved in protein assembly