General Histology Cells Smallest structures, varies in size,
shape and surface. Cells posses properties that permit:
Excitability nerve cells conduct an impulse Synthesis aiding in the
bodies function, such as glands Membrane transport nutrients are
transported Reproduction union of sperm and ovum can lead to the
formation of an offspring 2
Slide 3
Cell Junctions 3 Desmosomes cell-to-cell attachments; between
ameloblasts and cells of stratified squamous epithelium that lines
the oral cavity. Tight junctions cells attach to each other by
fusion of their cell membranes; adjacent odontoblasts form tight
junctions that prevent substances in the pulp from passing into the
dentin. Gap junctions channel that runs between cells for
communication of cell electrical impulses and passage for
molecules; present amount some odontoblasts, allowing to coordinate
their activity. Hemidesmosome attachment of a cell to a noncellular
surface; basal layer cells of stratified squamous epithelium attach
to the basement membrane by hemidesmosomes; present in epithelial
attachment of the tooth
Slide 4
4 The Cell
Slide 5
5 Cells are surrounded by a cell membrane that separates them
from the outside environment. 1. cytoplasm 2. organelles 3.
inclusions 4. nucleus Specialization A) differentiation cells that
recognize one another will group together B) organization of
chemicals chemicals appear earlier in the embryo. Endocrine
substances are produced by one type of cell and can affect other
types of cells C) Cells tissues organs organ systems
Slide 6
Cell Membrane 6 Cell membrane A) Called a plasma membrane or
plasmalemma; selectively permeable because it controls passage of
materials in and out of the cell. Uses active transport, passive
transport, or facilitated diffusion. Lipids and proteins are the
major components (3:2 ratio of proteins) Structure is trilaminar,
with bipolar membrane and a central core of lipids between two
layers of protein Diffusion of small lipid-insoluble
substances
Slide 7
7
Slide 8
Fluid Mosaic Model 8 Shown on the previous slide Trilaminar
structure composted of two facing layers of lipid molecules, into
which larger globular proteins are inserted. Lipid bilayers consist
mainly of phospholipid molecules; hydrophilic ends face the outer
and inner surfaces of the cell; the hydrophobic ends attract and
face each other. Globular proteins are integral proteins and
peripheral proteins. Integral extend through the full width of the
cell membrane and protrude and may have carbohydrate units attached
to them. Peripheral are linked or attached to the cell membrane
surface.
Slide 9
Cytoplasm 9 Translucent, aqueous, homogeneous gel enclosed in
the cell by the cell membrane. The cytoplasm has three major
elements; the cytosol, organelles and inclusions. All metabolic
activities of the cell occur in the cytoplasm which include:
Assimilation (digestion) Synthesis of substances such as proteins,
proteoglycans, and glycoproteins A transport medium in which all
nutrients and metabolites are carried from one organelle to another
Presence of enzymes and electrolytes where specific metabolic
reactions take place (glycolysis)
Slide 10
Nucleus 10 In cell biology, the nucleus is a membrane-enclosed
organelle found in eukaryotic cells. It contains most of the cell's
genetic material, organized as multiple long linear DNA molecules
in complex with a large variety of proteins, such as histones, to
form chromosomes. The genes within these chromosomes are the cell's
nuclear genome. The function of the nucleus is to maintain the
integrity of these genes and to control the activities of the cell
by regulating gene expression the nucleus is, therefore, the
control center of the cell. The main structures making up the
nucleus are the nuclear membrane, a double membrane that encloses
the entire organelle and isolates its contents from the cellular
cytoplasm, and the nucleoskeleton (which includes nuclear lamina),
a mesh work within the nucleus that adds mechanical support, much
like the cytoskeleton, which supports the cell as a whole.
Slide 11
Nucleus 11 Nuclear pores are required that regulate Nuclear
transport of molecules across the envelope. The pores cross both
nuclear membranes, providing a channel through which larger
molecules must be actively transported by carrier proteins while
allowing free movement of small molecules and ions. The interior of
the nucleus does not contain any membrane-bound sub compartments.
The best-known of these is the nucleolus, which is mainly involved
in the assembly of ribosomes. After being produced in the
nucleolus, ribosomes are exported to the cytoplasm where they
translate mRNA.
Slide 12
Synthesis Activities 12 Three types of RNA are necessary for
protein synthesis: Messenger RNA (mRNA) copies of short segments of
deoxyribonucleic acid (DNA) Contains all genetic information of
proteins Must pass through the ribosomes attached to the
endoplasmic reticulum As it passes through the ribosomes, transfer
RNA (tRNA) adds the exact amino acid to the newly forming proteins
Protein synthesis can also occur on polyribosomes floating freely
in the cytoplasm; proteins synthesized on the ribosomes attached to
the ER are transported out of the cell
Slide 13
13
Slide 14
Inclusions 14 Inclusions are nonliving metabolic by-products
found in the cytoplasm. May appear as lipid droplets, carbohydrate
accumulations, or engulfed foreign substances
Slide 15
Lysosomes 15 Intracellular digestion is carried out by
organelles called lysosomes. There are several contexts in which
cells need to carry out digestion. Include the recycling of
cellular organelles and the breakdown of viruses and other cellular
invaders. Single-celled organisms use lysosomes to digest their
food as they have no process for extracellular digestion. The pH
within a lysosome is very acidic and the enzymes within work most
effectively in this environment. The components of a lysosome have
evolved specific conformations that make them resistant to break
down by the enzymes within the lysosome. During phagocytosis,
lysosomes fuse with engulfed substances to form a secondary
vesicle; the vesicle may then remain in the cell as a residual body
or discharged outside the cell
Slide 16
Golgi Complex 16 The Golgi apparatus receives protein and/or
lipid-filled vesicles that bud from the ER. The Golgi apparatus
contains enzymes that modify proteins and lipids. For example, it
can add a chain of sugars to proteins and lipids, thereby making
them glycoproteins and glycolipids, which are molecules found in
the plasma membrane. The vesicles that leave the Golgi apparatus
move to other parts of the cell. Some vesicles proceed to the
plasma membrane where they discharge their contents. Because this
is secretion, note that the Golgi apparatus is involved in
processing, packaging, and secretion. Other vesicles that leave the
Golgi apparatus are lysosomes. The Golgi complex is the storage
site for newly synthesized proteins and of course packaging and
transporting many cell products. Also produces large carbohydrate
molecules and lysosomes.
Slide 17
Mitochondria 17 Although the size and shape of mitochondria
(sing., mitochondrion) can vary, all are bounded by a double
membrane. The inner membrane is folded to form little shelves
called cristae, which project into the matrix, an inner space
filled with a gel-like fluid. Mitochondria are the site of ATP
(adenosine triphosphate) production involving complex metabolic
pathways. As you know, ATP molecules are the common carrier of
energy in cells. A shorthand way to indicate the chemical
transformation that involves mitochondria.
Slide 18
Mitochondria Continued 18 Mitochondria are often called the
powerhouse of the cell: Just as a powerhouse burns fuel to produce
electricity, the mitochondria convert the chemical energy of
carbohydrate molecules into the chemical energy of ATP molecules.
In the process, mitochondria use up oxygen and give off carbon
dioxide and water. The oxygen you breathe in enters cells and then
mitochondria; the carbon dioxide you breathe out is released by
mitochondria. Because oxygen is used up and carbon dioxide is
released, we say that mitochondria carry on cellular
respiration.
Slide 19
Endoplasmic Reticulum 19 The endoplasmic reticulum (ER), a
complicated system of membranous channels and flattened vesicles,
is physically continuous with the outer membrane of the nuclear
envelope. Rough ER is studded with ribosomes on the side of the
membrane that faces the cytoplasm. Here proteins are synthesized
and enter the ER interior where processing and modification begin.
Some of these proteins are incorporated into membrane, and some are
for export. Smooth ER, which is continuous with rough ER, does not
have attached ribosomes. Smooth ER synthesizes the phospholipids
that occur in membranes and has various other functions, depending
on the particular cell. In the testes, it produces testosterone,
and in the liver it helps detoxify drugs. Regardless of any
specialized function, ER also forms vesicles in which large
molecules are transported to other parts of the cell. Often these
vesicles are on their way to the plasma membrane or the Golgi
apparatus.
Slide 20
Filaments and Tubules 20 Associated with contractility in cells
thread-like structures about 7-10nm thick Microfilaments act as a
support system for the cell cytoskeleton Bundles of microfilaments
form tonofibrils and become part of the attachment apparatus
between cells (desmosomes)
Slide 21
Microtubules 21 Delicate tubes, 20-27 nm wide, found in cells
that are undergoing mitosis and alterations in cell shape They have
an internal support function, especially in long cellular processes
such as neurites or odontoblastic processes They have the capacity
to direct intracellular transport through the cytoplasm
Slide 22
Centrioles 22 Cylindrical structures composed of microtubule
like components Centrioles function in cell replication and the
formation of cellular extensions
Slide 23
Internal Environment and Homeostasis 23 Extracellular fluid
Circulates outside and between cells Intracellular fluid Fluid
located inside the cells of the body Homeostasis The delicate
balance maintained between the two fluid compositions
Slide 24
Transport through the Cell Membrane 24 Diffusion - is the
random movement of simple atoms or molecules from area of higher
concentration to an area of lower concentration until they are
equally distributed. To illustrate diffusion, imagine putting a
tablet of dye into water. The water eventually takes on the color
of the dye as the dye molecules diffuse. The chemical and physical
properties of the plasma membrane allow only a few types of
molecules to enter and exit a cell by simple diffusion.
Lipid-soluble molecules such as alcohols can diffuse through the
membrane because lipids are the membranes main structural
components. Gases can also diffuse through the lipid bilayer; this
is the mechanism by which oxygen enters cells and carbon dioxide
exits cells. For example, consider the movement of oxygen from the
lungs to the bloodstream.
Slide 25
Transport Continued 25 When you inhale, oxygen fills the tiny
air sacs, or alveoli, within your lungs. Neighboring lung
capillaries contain red blood cells with a very low oxygen
concentration. Oxygen diffuses from the area of highest
concentration to the area of lowest concentration: first through
alveolar cells, then lung capillary cells, and finally into the red
blood cells. When atoms or molecules diffuse from areas of higher
to lower concentration across plasma membranes, no cellular energy
is involved. Instead, kinetic or thermal energy of matter is the
energy source for diffusion.
Slide 26
Osmosis 26 Osmosis is the diffusion of water across a plasma
membrane. Osmosis occurs whenever an unequal concentration of water
exists on either side of a selectively permeable membrane. (Recall
that a selectively permeable membrane allows water to pass freely,
but not most dissolved substances.) In a solution, water is more
concentrated when it contains fewer dissolved substances, or
solutes, (and thus is closest to pure water). Water is less
concentrated as solute concentration increases. Osmotic pressure is
the force exerted on a selectively permeable membrane because water
has moved from the area of higher water concentration to the area
of lower water concentration(higher concentration of solute).
Slide 27
Osmosis Continued 27 Tonicity is the degree to which a
solutions concentration of solute-versus-water causes water to move
into or out of cells. Normally, body fluids are isotonic to cells
that is, there is an equal concentration of solutes (dissolved
substances) and solvent (water) on both sides of the plasma
membrane, and cells maintain their usual size and shape. Medically
administered intravenous solutions usually have this tonicity. Body
fluids which are not isotonic to body cells are the result of
dehydration or water intoxication. Solutions (solute plus solvent)
that cause cells to swell or even to burst due to an intake of
water are said to be hypotonic solutions. If red blood cells are
placed in a hypotonic solution, which has a higher concentration of
water (lower concentration of solute) than do the cells, water
enters the cells and they swell.
Slide 28
Continued 28 The term lysis refers to disrupted cells:
hemolysis, then, is disrupted red blood cells. Solutions that cause
cells to shrink or to shrivel due to a loss of water are said to be
hypertonic solutions. If red blood cells are placed in a hypertonic
solution, which has a lower concentration of water (higher
concentration of solute) than do the cells, water leaves the cells
and they shrink.
Slide 29
29
Slide 30
Active Transport 30 Process used by the cell when large
quantities of a substance are needed inside the cell and only a
small amount of the substance is present in the extracellular
fluid. Pumps the substance against its concentration gradient. ATP
Sodium pump; important for the transmission of nerve impulses
Almost all monosaccharides are actively transported into the body.
Phagocytosis movement of a solid particle into the cell Pinocytosis
movement of fluid into a cell, the cell invaginates around
fluid
Slide 31
31
Slide 32
32 The Cell Cycle
Slide 33
33
Slide 34
Cell Replication - Mitosis 34 Interphase: During interphase,
the cell carries on its regular activities, and it also gets ready
to divide if it is going to complete the cell cycle. For these
cells, interphase has three stages, called G1 phase, S phase, and
G2 phase. G1 Phase - it is best to think of G as standing for
growth. Protein synthesis is very much a part of these growth
phases. During G1, a cell doubles its organelles (such as
mitochondria and ribosomes) and accumulates materials that will be
used for DNA synthesis.
Slide 35
Continued 35 S Phase Following G1, the cell enters the S (for
synthesis) phase. During the S phase, DNA replication occurs. At
the beginning of the S phase, each chromosome is composed of one
DNA double helix, which is equal to a chromatid. At the end of this
phase, each chromosome has two identical DNA double helix
molecules, and therefore is composed of two sister chromatids.
Another way of expressing these events is to say that DNA
replication has resulted in duplicated chromosomes. G2 Phase During
this phase, the cell synthesizes proteins that will assist cell
division, such as the protein found in microtubules. The role of
microtubules in cell division is described later in this
section.
Slide 36
Prophase 36 Several events occur during prophase that visibly
indicate the cell is about to divide. The two pairs of centrioles
outside the nucleus begin moving away from each other toward
opposite ends of the nucleus. Spindle fibers appear between the
separating centriole pairs, the nuclear envelope begins to
fragment, and the nucleolus begins to disappear. The chromosomes
are now fully visible. Spindle fibers attach to the centromeres as
the chromosomes continue to shorten and thicken. During prophase,
chromosomes are randomly placed in the nucleus.
Slide 37
Prophase Continued 37 At the end of prophase, a cell has a
fully formed spindle. A spindle has poles, asters, and fibers. The
asters are arrays of short microtubules that radiate from the poles
and the fibers are bundles of microtubules that stretch between the
poles. (A spindle resembles a lopsided bicycle wheel; the asters
are the spokes.) Centrioles are located in centrosomes, at opposite
poles of the cell. Centrosomes are believed to organize the
spindle.
Slide 38
Metaphase 38 During metaphase, the nuclear envelope is
fragmented, and the spindle occupies the region formerly occupied
by the nucleus. The paired chromosomes are now at the equator
(center) of the spindle. Metaphase is characterized by a fully
formed spindle, and the chromosomes, each with two sister
chromatids, are aligned at the equator
Slide 39
Anaphase 39 At the start of anaphase, the sister chromatids
separate. Once separated, the chromatids are called chromosomes.
Separation of the sister chromatids ensures that each cell receives
a copy of each type of chromosome and thereby has a full complement
of genes. During anaphase, the daughter chromosomes move to the
poles of the spindle. Anaphase is characterized by the movement of
chromosomes toward each pole and thus, to opposite sides of the
cell.
Slide 40
Telophase 40 A nuclear membrane forms around each set of
chromosomes Centrioles replicate in each cell
Slide 41
Dental Tissues 41 Organelles play an important role in
providing energy (mitochondria) which helps in calcifying dental
tissues Cell organelles help maintain tissues after the initial
formation by the cell; fibroblasts contain increased numbers of
cell organelles; these additional organelles aid fibroblasts in
their synthesizing and secretory functions
Slide 42
Basic Tissues 42 Individual cells multiply and differentiate to
perform specialized functions; groups of cells with similar
characteristics and functions come together and form tissues.
Tissue components Cells Intercellular substance product of living
cells, passageway Tissue Fluid blood plasma that transports
Slide 43
Tissues in the Human Body 43 1.epithelial tissues
(covering/lining); 2.connective tissues (support); 3.muscle tissues
(movement); 4.nervous tissues (control).
Slide 44
Epithelial Tissue 44 Many epithelial tissues are classified
according to their shape and the number of layers they possess:
Some terms used to describe epithelia include: a. simple = single
layer of cells; b. stratified = many layers of cells; c. squamous =
flattened cells; d. cuboidal = square-shaped cells; e. columnar =
elongated cells (i.e. taller than wide);
Slide 45
Types of Simple Epithelium 45 Simple squamous epithelium: a
single layer of flattened cells; generally allows for easy passage
(diffusion) of substances; Locations: 1.lining air sacs of lungs,
2.lining capillaries, 3.lining body cavities, 4.covering ventral
organs;
Slide 46
Simple Cuboidal Epithelium 46 Simple cuboidal epithelium: a
single layer of square-shaped cells with large centrally located
nuclei; Functions: 1.secretion 2.absorption; Locations: 1.lining
kidney tubules, 2.lining ducts of glands, 3.covering surface of
ovary;
Slide 47
Simple Columnar Epithelium 47 A single layer of elongated cells
with basally located nuclei (near basement membrane); 1.protection,
2.absorption, 3.secretion; 1.lining small intestine, 2.lining
uterus; Free Surface Modifications: 1.microvilli (increase surface
area) 2.goblet cells (secrete protective mucus);
Slide 48
Pseudostratified Columnar Epithelium 48 Pseudostratified
columnar epithelium: a single layer of elongated cells with
scattered nuclei (i.e. look stratified but are not); all cells
touch the basement membrane Functions: 1.secretion, 2.protection;
Locations: 1.lining trachea, 2.lining fallopian tube; Free surface
modifications: 1.cilia (trap debris and aid in passage of mucus up
and out of airway); 2.goblet cells (produce mucus which coats cilia
and helps trap debris).
Slide 49
Stratified Epithelium 49 Stratified squamous epithelium: many
layers of flattened cells; Function = protection; Locations:
Non-keratinized: 1.lining mouth, 2.lining throat, Keratinized
epidermis of the skin
Stratified Columnar Epithelium 51 Stratified columnar
epithelium: 2-3 layers of elongated cells Locations 1.vas deferens
2.part of male urethra Transitional epithelium: many layers of
cells that change shape in response to tension; Function =
distensibility (i.e. stretches easily to allow urine to fill
bladder); Location = lining urinary bladder and ureters.
Slide 52
Glandular Epithelium 52 Glandular Epithelium a.usually simple
cuboidal columnar ET; b.Function = secretion; c.two major types:
Exocrine glands secrete products into a duct, which opens onto: an
external surface (i.e sweat gland) or an internal space/lumen (i.e.
gastric gland);
Slide 53
Glandular Epithelium Continues 53 Endocrine glands secrete
hormones into the blood. d.Exocrine glands structure varies
tremendously Single cells (unicellular) goblet cells Many cells
(multicellular) Simple unbranched Compound branched Tubular
tube-like Alveolar sac-like e.Exocrine glandular secretions are
classified according to whether they consist of cellular products
or portions of glandular cells:
Slide 54
Continued 54 Three types of secretions. Merocrine: secrete
fluid through cell membranes into a duct with no loss of glandular
cells. Example = salivary glands. Apocrine: lose small portion of
cells with secretion. Example = mammary glands; Holocrine: release
entire cells into secretion. Example = sebaceous glands in skin
(oil).
Slide 55
Connective Tissue 55 Ground Substance: a.amorphous material
that fills the space between cells and fibers; b.Functions as a
molecular "sieve" through which nutrients and gases can diffuse
between cells and blood capillaries.
Slide 56
Major Cell Types 56 Major Cell Types: 1.fixed cell in each CT
type: maintains constant numbers a.fibroblasts in CT proper
b.osteocyte in bone, c.chondrocyte in cartilage. d.blast cells =
undifferentiated cells that secrete matrix; fibroblast in CT
proper, chondroblast in cartilage; osteoblast in bone;
Slide 57
Wandering Cells 57 wandering cells; are not always there
a.migrating white blood cells that respond to tissue damage (i.e.
inflammation) ; 2 types: mast cells: Secrete heparin to prevent
excessive blood clotting Secrete histamine to promote inflammation
macrophages or phagocytes:See Fig 5.14, page 142. Eat foreign
material
Slide 58
Connective Tissues 58 Connective Tissue Fibers = 3 types:
1.Collagen fibers are composed of the protein collagen. a.provide
high tensile strength to matrix; b.stain pink. 2.Elastic fibers are
composed of the protein elastin. a.provide rubbery resiliency to
matrix; b.stain purple; c.found in skin, lungs, and blood
vessels.
Slide 59
Continued 59 3. Reticular fibers are fine collagenous fibers.
a.form delicate networks; b.found in basement membranes; c.stain
purple.
Slide 60
Categories of Connective Tissues 60 Embryonic CT = mesenchyme:
from mesoderm a. Location = embryo; b. Function = gives rise to all
other types of CT; 2. Connective Tissue Proper All CT with a semi-
fluid ground substance a.Loose Areolar CT: gel-like matrix with
fibroblasts, macrophages, mast cells and collagen and elastic
fibers; Location = beneath epithelium, covering ventral organs;
Functions = diffusion of nutrients and gases; wraps & cushions
organs.
Slide 61
Continued 61 Connective Tissue Proper b. Adipose Tissue:
closely packed adipocytes (fat-cells) with nuclei pushed to one
side within matrix (resemble signet rings); Location = under skin
(as subcutaneous layer), around kidneys and eyeballs, breasts;
Functions = energy store, insulation, protection;
Slide 62
Continued 62 Reticular CT: network of reticular fibers within
loose ground substance and reticulocytes. Location = basement
membranes and lymphatic organs (i.e. lymph nodes, thymus, spleen);
Function = support; Dense Regular CT (White Fibrous CT): primarily
collagen fibers (pink) with few fibroblasts (you can only see
nuclei!); Location = tendons, ligaments; Functions = attachment,
tensile strength; Poor blood supply = slow to no healing; Dense
Irregular CT: primarily collagen fibers randomly arranged; Location
= dermis of skin, heart valves; Function = provides tensile
strength; Elastic CT: primarily elastin fibers (purple); Location =
lung tissue, wall of aorta; Function = durability with
stretch;
Slide 63
Special Connective Tissue 63 Hyaline cartilage: amorphous
(chondroitin and glucosamine) matrix that surrounds cells =
chondrocytes (within lacunae); Locations = embryonic skeleton,
costal cartilages, cartilage of the nose, trachea, and larynx;
Function = support; Avascular = no healing. Elastic cartilage: same
as above plus elastic fibers (purple); Locations = external ear,
epiglottis; Functions = maintenance of shape plus flexibility;
Fibrocartilage: less firm than above; Locations = intervertebral
discs, pubic symphysis; Functions = tensile strength plus shock
absorber;
Slide 64
Continued 64 Bone: hard, calcified matrix ([Ca 3 (PO 4 ) 2.
(OH) 2 ] = rigidity), with collagen fibers (tensile strength) and
cells = osteocytes (within lacunae); Location = bones of the
skeleton; Functions = protection, support, movement, calcium store
and hematopoiesis; Highly vascular = fast healing; Blood: red cells
(erythrocytes), white cells (leukocytes), and platelets
(thrombocytes) in a fluid matrix called plasma; Location = within
heart and blood vessels; Function = transport of gases, nutrients,
wastes.
Slide 65
Types of Muscle Tissue 65 1. Skeletal Muscle Tissue
a.Structure: long thin cells (fibers) with many nuclei; alternating
areas of light & dark (striations); Location: attached to
bones; Function: move bones of skeleton; Control: voluntary =
conscious. 2. Cardiac Muscle Tissue a.Structure: network of cells
with one centrally located nucleus; intercalated discs (where 2
cells meet); striations; Location:heart; Function:to pump blood
from heart -----> lungs; to pump blood from heart ----->
body; Control: involuntary = unconscious.
Slide 66
Continued 66 3. Smooth Muscle Tissue a.Structure:
spindle-shaped cells with one centrally located nucleus; no
striations; Location: walls of hollow visceral organs; walls of
blood vessels; attached to hair follicles in the dermis Function:
movement of food through digestive tract; vasoconstriction;
Control: involuntary = unconscious.
Slide 67
Nerve Tissue 67 1. Primary cells = neurons which respond to
changes in their surroundings (stimuli); 2.neurons are surrounded
by neuroglia (supporting cells); B.Locations: Brain, Spinal Cord,
Nerves C.Function: Coordination or integration of body parts (i.e.
to transmit signals from body parts to brain and from brain back to
body parts); No reproduction of neurons, only neuroglia can
divide.
Slide 68
Epithelial Membranes 68 DEFINITION: An epithelial membrane is a
continuous multicellular sheet composed of at least two primary
types of tissue: an epithelium bound to a discrete underlying CT
tissue. B. Three Common Types: 1.Cutaneous Membrane: a.skin;
consists of keratinized stratified squamous ET firmly attached to a
thick layer of dense irregular CT. 2.Mucous Membranes (mucosae): a.
line body cavities that open to the outside; b. include lining of
digestive, respiratory and urinary tract; c. are "wet" or moist
membranes (through secretions of mucus); d. consist of a layer of
epithelium (varies depending upon location) firmly attached to a
layer of loose areolar CT.
Slide 69
Three Common Types 69 Serous Membranes (serosae): a.are found
in closed ventral body cavities; b.consist of two layers with a
potential space (cavity) between them: visceral membrane surrounds
an organ; parietal membrane lines a body cavity; c.secrete a thin
watery fluid called serous fluid into the cavity between the
membranes; function = lubrication; d.each membrane consists of a
thin layer of simple squamous ET resting on a thin layer of areolar
(loose) CT; e.are named for the organs that occupy each cavity:
pleural = lungs; pericardial = heart; peritoneal = abdominal
organs.