Oral histology LO 4.

Histio

This prefix means that something is relating to tissue.

Logia(ology)

This suffix means "the study of"

Microanatomy

Histology used to be called:

Histology

18th century ——————— became a separate branch of science: establishing the normal structures of tissues and cells in relationships to their function. Based upon th examination of samples of cells and tissue.

100 um

The human eye has a resolution of about ——— um. A plant cell is one of the only cells that can be seen by the human eye.

Light microscope

Cells observed under this type of microscope cab be alive or fixed and stained. This type of microscope can magnify up to 1000 times the size of an object.

Blue (or purple)

Acidic containing structures like nuclei are stained with hematoxylin. The colour is:

Red (or fuscia)

Alkaline substances like cytoplasm are stained with eosin. The colour is:

Electron microscope

This type of microscope was invented in the first half of the 20th century. Distinguishes individual molecules of biological importance. In effect, it can magnify objects up to 1 million times. This type of microscopes cannot be used on living things, it will kill them. The ——————— are transmitted through a thin specimen in a vacuum. Images are projected into a fluorescent screen.

Nanometer

This measurement is 1 billionth of a meter.

Angstrom

This measurement is 0.1 of a nanometer.

Scanning electron microscope

To use this type of microscope, the specimen must be fixed, dried, and coated with a thin layer of heavy metal (gold or platinum). An ——————— beam is reflected from the surface of the coated specimen. As tissue is scanned by a focused beam of electrons, the electrons are converted into an image onto a screen.

210

There are about ——— known distinct human cell types, the body is comprised of 100 trillion cells.

Red blood cells

All human cells have a nucleus except for this type of cell:

Nucleus

This organelle has a double layered nuclear membrane with pores. Contains 1 or more nucleoli: DNA

Plasmalemma

This organelle is a thin, flexible, dynamic barrier between the organized living particles within the cell and outside the cell. A selective barrier: responsible for maintaining the difference between the external and internal environment of the cell (homeostasis). Has 3 layers (trilaminar)

Outer surface

This layer of the plasmalemma contains glycoproteins: receptors for hormones and neurotransmitters.

Central layer

This layer of the plasmalemma contains phospholipids: barrier for diffusion.

Inner surface

This layer of the plasmalemma contains proteins: 60%-70% of total mass, structural reinforcement.

Rough endoplasmic reticulum (rough ER)

The structure of this organelle: series of interlocking membrane-bound canals in a pattern of flattened long, branching tubules with ribosomes on their cytoplasmic face.

Function: synthesis and distribution of proteins for export (collagen from fibroblasts, and digestive enzymes from pancreas).

Smooth endoplasmic reticulum (smooth ER)

Function of this organelle: tubular network free of ribosomes. Function: synthesis of steroids, and degradation of hormones and drugs.

Mitochondria

The electron microscope reveals the structure of this organelle as: trilaminar (3 layers) and membranous. Function: obtains energy by enzymatic action and then converts it to ATP for cellular use.

Golgi complex (or apparatus)

Structure of this organelle: electron microscope reveals it has 6-8 smooth surface membranes , cavities filled with fluid and expand during secretory activity. Function: protein formation and secretion.

Lysosomes

For this organelle, the structure is related to function. Shape and density vary greatly. Budding vesicle on the maturing face of the Golgi body. Contains digestive enzymes. Digestion of worn out cells (autophagocytic).

Microvilli

These organelles are specialized structures that appear on the free surface of some epithelial cells, extensions of the plasmalemma. Microscopic finger-like projections increase the absorptive surface area up to 30X. Part of taste bud: taste hairs. Modification to increase surface area of intestines.

Exocytosis

This is a cellular transport mechanism. Active transport from a vesicle within the cell to the extracellular environment, fusion of the vesicle membrane with the cell membrane.

Endocytosis

This is a cellular transport mechanism. Uptake of material from the extracellular environment.

Phagocytosis

This is a cellular transport mechanism. Moving cell engulfs/digests material from extracellular environment. Ex. WBC engulfed bacteria.

Pinocytosis

This is a cellular transport mechanism. Stationary cell engulfs/digests material from extracellular environment. Ex. Kidney tubules reabsorb proteins.

Mitosis

This is cell division.

Microtubules

Structure of this organelle: formed by proteins, slender, hollow, cylindrical structures, diameter of about 25 nm, nonmembranous cellular organelles.

Function: act as a scaffold to determine cell shape, building block of the cell. Guidance system in intracellular transport: provides a set of "tracks" for cell organelles and vesicles to move on. These are located in the cytoskeleton. Support of cilia.

Kartagener's syndrome

Defects in the cilia and flagella of human cells are associated with some notable medical problems such as ———————— ———————: portions of the microtubules are not connected properly, this is characterized by recurrent respiratory infections related to the inability of cilia in the respiratory tract to clear away bacteria and other materials.

Microtubules

These are the framework of centrioles (9 sets of triplets).

Mitotic spindle fibres

Spindle fibres for separating chromosomes during mitosis.

Microfilaments

Structure: thin threadlike proteins: filamentous cytoplasmic, diameters vary 5-7nm.

Structure: predominantly composed of contractile protein: actin. Most abundant cellular protein, carry out cellular movements including sliding and contraction.

Function: contraction and support all cells except RBC, cellular movements including gliding and contraction.

Microfilaments

Tonofilaments of hemidesmosomes and desmosomes, mechanical and structural function (attachment apparatus).

Cytoplasmic inclusions

In addition to organelles, there is a wide variety of cellular inclusions.

-endogenous inclusions

-exogenous inclusions

Not present in all cells, maybe present in specific cells during certain physiological activities.

Endogenous inclusions

——————— inclusions: generally essential to life. Arise from within the cell.

-lipid droplets (fat storage)

- some pigments

Melanin

Most abundant and important pigment. Origin: neural crest cells produced by melanocytes. Pigment transferred to basal epidermal cells to screen out harmful overexposure to UV light.

Exogenous inclusions

Transitory and often harmful, arise outside the cell. Incorperated by phagocytosis, pinocytosis, absorption: heavy metals, lead poisoning, asbestos, and carbon.