Download Cellular anatomy Tissues types

Cellular anatomy
Tissues types
Levels of organization…
 Cells  Tissues
 Tissues  Organs
Cellular Anatomy
 Cell organelles
Cellular Anatomy
 Selected human cell structures
 Nucleus: DNA’s home
Cellular Anatomy
 Selected human cell structures
 Ribosomes, endoplasmic
reticulum & Golgi apparatus:
protein builders
Cellular Anatomy
 Selected human cell structures
 Lysosomes: digesters
Cellular Anatomy
 Selected human cell structures
 Mitochondria:
ATP factories
Cellular Anatomy
 Selected human cell structures
 Plasma membrane


Selectively-permeable
Membrane proteins
Membrane Transport
 Diffusion
 Filtration
 Facilitated diffusion
 Active transport
 Endocytosis
 Exocytosis
Tissue Types
 Epithelium: Covering/lining
 Secretion, absorption, filtration, diffusion
Tissue Types
 Connective tissue: Connects/supports
Tissue Types
 Muscular tissue: Contracts to cause movement
Tissue Types
 Nervous tissue: Sends electrochemical messages
Cellular anatomy
Tissues types
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Levels of organization…
 Cells  Tissues
 Tissues  Organs
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We’ll be spending the next several days looking at tissues. As a reminder, a tissue is a
collection of cells doing the same job together. Two or more different types of
tissues working together make up an organ. This picture shows a cross-section of
skin (an organ). The superficial layers (stained purple) are epithelium. Notice that the
epithelium consists of many cells clustered close-together. The deeper pink-staining
region is connective tissue. There are fewer cells in connective tissue.
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Cellular Anatomy
 Cell organelles
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Think back to your biology class. You may remember that cells are the basic units of
life. That means that cells are small units that demonstrate all of life’s processes, and
that all living things are made up of cells. Each cell has many structures, called
organelles, inside of it that carry out the cell’s life processes.
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Cellular Anatomy
 Selected human cell structures
 Nucleus: DNA’s home
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At some point in their lives, all cells have at least one nucleus. Most mature cells
have exactly one nucleus, though there are expections. Mature red blood cells have
no nucleus, for example, while skeletal muscle cells have many nuclei. The nucleus
houses the cell’s DNA, which has the instructions for what molecules the cell can
make. The DNA in each cell is identical, but different cells might have different parts
of the DNA “turned on.” This is why the nucleus, with its DNA, can be considered the
“director” of a cell’s activity.
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Cellular Anatomy
 Selected human cell structures
 Ribosomes, endoplasmic
reticulum & Golgi apparatus:
protein builders
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I’ve included these three structures together because they’re all involved in the
same process: manufacturing molecules and preparing them for secretion.
Ribosomes manufacture proteins while endoplasmic reticulum manufactures lipidbased molecules. The ER is also involved in moving newly-made substances to the
Golgi apparatus, which then packages the substances into vesicles. Many vesicles are
secretory vesicles, which remain in the cell until the cell is ready to secrete the
molecules. Then, the vesicles fuse with the plasma membrane and release their
contents outside the cell.
Cells that do a lot of secretion (e.g. glandular cells) will have large amounts of ER and
Golgi apparatus.
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Cellular Anatomy
 Selected human cell structures
 Lysosomes: digesters
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Lysosomes are large vesicles (made by the Golgi apparatus) filled with digestive
enzymes. Their job is to fuse with other things inside the cell – food vacuoles, wornout cell parts, or engulfed bacteria – and digest them, effectively using those
particles as food for the cell. Lysosomes also play a role in cell suicide. If they release
their digestive enzymes near the plasma membrane, the cell may burst and die.
Cells involved in absorption and digestion, such as macrophages which engulf
invading bacteria, have many lysosomes.
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Cellular Anatomy
 Selected human cell structures
 Mitochondria:
ATP factories
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Mitochondria are the “powerhouses” of a cell. They carry out aerobic respiration
which uses oxygen to “burn” simple sugars and make large amounts of ATP. ATP is a
useable form of chemical energy which is used to power the chemical reactions
inside cells. Cells can produce a small amount of ATP anaerobically (without oxygen)
in the cytoplasm, but this doesn’t yield nearly enough ATP to run all of the chemical
reactions to support life in human cells.
Cells that require a lot of ATP, such as muscle cells, will have huge numbers of
mitochondria.
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Cellular Anatomy
 Selected human cell structures
 Plasma membrane


Selectively-permeable
Membrane proteins
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The plasma membrane is the “skin” of a cell. It separates the cell’s cytoplasm and
intracellular fluid from the interstitial fluid on the outside. It is made of two layers of
phospholipids – molecules that have a polar end and a nonpolar end. The plasma
membrane is selectively-permeable, which means that some substances can move
across it freely while others cannot. Generally, nonpolar molecules and very small
substances can diffuse across the membrane while large or polar molecules cannot.
There are many different types of membrane proteins embedded in the plasma
membrane. These proteins carry out many functions, such as identifying the cell,
activating enzymes inside the cell, responding to chemical signals, and transport. The
transport proteins are involved in moving substances into and out of the cell that
cannot otherwise cross the selectively-permeable membrane.
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Membrane Transport
 Diffusion
 Filtration
 Facilitated diffusion
 Active transport
 Endocytosis
 Exocytosis
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The most important cell process to our class is membrane transport – moving
substances across the plasma membrane between the cytoplasm and the interstitial
fluid. There are several ways this happens.
•Diffusion: Diffusion is one of the most fundamental laws of physics. Substances will
always tend to spread out from an area where they are highly-concentrated to an
area where they are less-concentrated. For molecules that can cross the plasma
membrane, diffusion can also happen across the membrane. For example, oxygen
gas is a nonpolar molecule and can easily move across the cell membrane. If there is
a high concentration of oxygen outside a cell, and less inside the cell, the oxygen can
just passively diffuse into the cell. Carbon dioxide is another gas that is nonpolar and
can diffuse across the membrane. Diffusion does not require any energy. It just
happens.
•Filtration is another type of movement directly across the plasma membrane. It is
different from diffusion, though, because pressure can cause molecules to move
against their concentration gradient. In other words, molecules such as water can be
forced to move from an area where there is little water to an area where there is
already a lot. Filtration occurs in the kidneys.
•Facilitated diffusion is just like simple diffusion above, except that it can happen
with molecules that cannot cross the plasma membrane. For this to happen, there
has to be an open transport protein in the membrane that allows the molecule to
pass. Think of these transport proteins like tunnels through a mountain or doors in a
wall. As long as the tunnel or door is open, diffusion can happen through them, even
though the molecules can’t go straight across the membrane otherwise.
•Active transport is the opposite of diffusion in almost every way. Active transport
actively pumps molecules across the plasma membrane, often against the
concentration gradient. This requires ATP energy to power the pumps. In fact, most
of the ATP used by some cells goes to powering active transport pumps.
•Endocytosis is a way of bringing large particles (food or bacteria, for example) into
a cell. The cell bends its plasma membrane around the particle, complely engulfing it
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Tissue Types
 Epithelium: Covering/lining
 Secretion, absorption, filtration, diffusion
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Recall that there are four types of tissues. Epithelial tissue (or epithelium) is a tissue
that covers or lines all of the body’s internal and external surfaces. The epidermis of
the skin is epithelium. Mucous membranes line all of the body’s cavities that open to
the outside world (oral cavity, nasal cavity, stomach, rectum, etc.). Serous
membranes line the body’s internal cavities.
Which each epithelial tissue generally carries out just one job, there are several jobs
that epithelium is well-suited for. Some epithelial tissues, called glands, secrete
chemicals onto surfaces, into cavities, or into the blood. Some absorb and digest
nutrients. Others pass materials from blood to underlying tissues through diffusion
or filtration.
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Tissue Types
 Connective tissue: Connects/supports
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Connective tissue joins various tissue types together and provides support and
protection to many other tissues. Examples of connective tissue include the bones,
cartilages, blood, and fat cells. Compared to epithelium, connective tissue has far
fewer cells and much more non-living extracellular matrix.
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Tissue Types
 Muscular tissue: Contracts to cause movement
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Muscular tissue is unique because it can shorten to cause movement. This includes
both skeletal movement (movement of the bones and facial features) as well as
visceral movement (movement of substances through the body).
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Tissue Types
 Nervous tissue: Sends electrochemical messages
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Nervous tissue is responsible for fast communication throughout the body. By
sending electrochemical impulses between the body’s periphery and the central
nervous system (the brain and spinal cord), we are able to be aware of our
environment and respond to changes in the environment.
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