Cells

The smallest unit of the human body is the cell. Although there are a number of different types of cells, all of them share certain characteristics, one of them being metabolism. Metabolism is the act of converting energy by continually building up substances by anabolism and breaking down substances by catabolism for use by the body. Metabolism can be described as an equation:

< ?xml:namespace prefix = "mml" />Metabolism=Anabolism+Catabolism

See Fig. 2-1 for an illustration of a cell and the corresponding table below for a brief description of the pictured organelles and their functions.

Tissues

There are four major categories of tissues. Within each type, the tissue either supports (stromal tissue) or does the actual work (parenchymal tissue) of the organ. For example, parenchymal nerve cells are the neurons that conduct the nervous impulse. Neuroglia are stromal nerve cells that enhance and support the functions of the nervous system. The four types of tissue include the following:

When tissue is destroyed by disease or trauma, the possibility of tissue replacement may be an option. Autologous tissue is that which is taken from one part of an individual’s body and is transplanted to another location. Auto- means “self.” An example would be a vein that is used to bypass a blocked coronary artery. If nonautologous tissue is used, it would mean that it is not from one’s self, but from another human. A synonym for nonautologous is allogenic, this time referring to being produced by a different human being. Allo- means “different.” Zooplastic tissue is that which is derived from an animal, for example, a cow or pig heart valve that is used to temporarily replace a structure until human donor tissue is available. Zo/o means “animal.” If tissue is syngeneic, as in the case of identical twins, it refers to a genetically identical individual. Syn- means “together or joined,” as in the sharing of the same DNA. Synonyms for the term syngeneic are isoplastic, isogeneic, and isologous. The combining form is/o means “equal.” Note that the synonyms use all of the previous suffixes: -plastic, -geneic, and -logous.

Organs

Organs, also referred to as viscera (sing. viscus), are arrangements of various types of tissue that accomplish specific purposes. The heart, for example, is made up of muscle tissue, called myocardium, and it is lined with epithelial tissue known as endocardium. Organs are grouped within body systems but do have specific terms to describe their parts.

Parts of Organs

Organs can be divided into parts and have a set of terms that describe these various parts.

organ = viscer/o

myocardium

 myocardi/o = heart muscle

 -um = structure

endocardium

 endocardi/o = within the heart

 -um = structure

Parts of Organs

	Term	Combining Form	Definition
	apex	apic/o	The pointed extremity of a conical structure (pl. apices).
	body (corporis)	corpor/o, som/o, somat/o	The largest or most important part of an organ.
	fornix	fornic/o	Any vaultlike or arched structure (pl. fornices).
	fundus	fund/o	The base or deepest part of a hollow organ that is farthest from the mouth of the organ (pl. fundi).
	hilum	hil/o	Recess, exit, or entrance of a duct into a gland, or of a nerve and vessels into an organ (pl. hila).
	lumen	lumin/o	The space within an artery, vein, intestine, or tube (pl. lumina).
	sinus	sin/o, sinus/o	A cavity or channel in bone, a dilated channel for blood, or a cavity that permits the escape of purulent (pus-filled) material (pl. sinuses). Antrum (pl. antra) and sinus are synonyms.
	vestibule	vestibul/o	A small space or cavity at the beginning of a canal.

 Exercise 1:

Intracellular Functions

Match each cell part with its function.

____ 1. mitochondria ____ 2. ribosomes ____ 3. nucleus ____ 4. lysosomes ____ 5. cytoplasm

A control center of cell

B holds organelles of cell

C digestive function

D responsible for energy production

E formation of proteins

Dorsal Cavities

The cranial cavity contains the brain and is surrounded and protected by the cranium, or skull. The spinal cavity contains the spinal cord and is surrounded and protected by the bones of the spine, or vertebrae.

Ventral Cavities

The thoracic cavity contains the heart, lungs, esophagus, and trachea (windpipe) and is protected by the ribs, the sternum (breastbone), and the vertebrae (backbones). This chest cavity is further divided into the two pleural cavities that contain the lungs; the mediastinum, the space between the lungs; and the pericardial cavity, which holds the heart.

The pleura is a double-folded serous (watery) membrane that provides a small amount of lubrication that allows the lungs to contract and expand with minimal friction. The side of the membrane that is closest to the lung is called the visceral pleura, whereas the side that is closest to the body wall is the parietal pleura.

The pericardial cavity shares a similar structure to the pleural cavity, again having a double-folded serous membrane designed to avoid friction on the organ that it encloses. This time the inner membrane is termed the visceral pericardium, whereas the outer membrane is the parietal pericardium.

The abdominopelvic cavity is composed of two cavities (abdominal and pelvic) that are not separated by any physical structure. Because nothing physically separates the abdominal and pelvic cavities, they are often collectively referred to as the abdominopelvic cavity.

The abdominal cavity contains the stomach, liver, gallbladder, pancreas, spleen, and intestines, whereas the pelvic cavity contains the bladder and reproductive organs. The only anterior protections for the abdominal cavity are the skin and muscles covering it, and in the back, just the vertebrae. It is separated from the thoracic cavity by a broad dome-shaped muscle called the diaphragm.

The pelvic cavity contains the bladder and reproductive organs. These organs are cradled on the sides and in the back by the pelvic bones.

The entire abdominopelvic cavity is lined with yet another serous membrane called the peritoneum. The parietal layer of the peritoneum lines the abdominopelvic cavity, whereas the visceral layer surrounds its organs. The term parietal is derived from a Latin term for “the wall”; hence this layer is always the one closest to the body wall. The visceral layer of the peritoneum (or pericardium) is the one that is closest to the organ or organs that it encloses. The greater and lesser omenta are extensions of the visceral peritoneum that hold and support the cavity’s organs. The fold of the peritoneum that joins the parietal and visceral layers and attaches it to the posterior wall of the abdominal cavity is called the mesentery.

Abdominopelvic Regions

The abdominopelvic regions are the nine regions that lie over the abdominopelvic cavity (Fig. 2-6). The area in the center of the abdominopelvic region is called the umbilical area. Laterally, to the left and right of this area, are the lumbar regions. They are called the lumbar regions because they are bound by the lumbar vertebrae. Superior to the lumbar regions, and below the ribs, are the hypochondriac regions. Medial to the hypochondriac regions, and superior to the umbilical region, is the epigastric region. Inferior to the umbilical region is the hypogastric region, and lateral to the sides of the hypogastric region are, respectively, the right and left iliac regions, sometimes referred to as the inguinal regions.

Abdominopelvic Quadrants

A simpler method of naming a location in the abdominopelvic area is to divide the area into quadrants, using the navel as the intersection. These quadrants are referred to as either right or left, upper or lower (Fig. 2-7). In the right upper quadrant (RUQ) lies the liver. In the left upper quadrant (LUQ) lie the stomach and the spleen. The appendix is in the right lower quadrant (RLQ). If a patient complains of pain in the area of McBurney’s point, the area that is approximately two thirds of the distance between the navel and the hip bone in the RLQ, appendicitis is suspected. Except for the appendix, the left lower quadrant (LLQ) contains organs similar to the lower right. In the LLQ, halfway between the navel and the hip bone, is Munro’s point. This is a standard site of entrance for surgeons who perform laparoscopic surgery.