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uitgebreide Samenvatting hoofdstuk 1 en 2 silverthorn human physiology
Uitgebreide samenvatting van hoofdstuk 1 en 2 van het boek human physiology van silverthorn
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Ch 3 human physiology FleurCh. 3 – Compartmentation: Cells and Tissues
Compartments in human body have both advantages as disadvantages
- Advantage: separates biochemical processes that might otherwise conflict with one
another.bv. intracellular compartment lysosome with internal pH of 5 would damage
cells if disrupted
- Disadvantage: barriers in between can make difficult to move needed materials from
one compartment to another. Specialized mechanisms for transport are needed.
Biological compartments come with a lot of anatomic variability – from totally enclosed
structures to structures without visible walls.
The first biological compartment was a cell, whose ICF was separated from the environment
by the plasma membrane. As evolution progressed, more compartments started to exist
within a cell, and within multicellular organisms.
3.1 functional compartments of the body
The human body is a complex compartment separated from the outside
world by a layers of cells. It is divided into three cavities:
Cranial cavity (Skull). Contains brain (=primary control center)
Thoracic cavity (thorax, bound by spine and ribs on top and sides,
and muscular diaphragm forms floor. It contains heart, which is
enclosed by pericardial sac and 2 lungs in pleural sacs)
Abdominopelvic cavity. Peritoneum lines the abdomen and
surrounds organs within it (stomach, intestines, liver, pancreas,
gallbladder, spleen)
Kidneys lie outside of abdominal cavity, between peritoneum and
muscles/bones of back.
Pelvis contains reproductive organs: urinary bladder, and terminal portion of
large intestine.
These cavities are separated from one another by bones and tissues and are lined
with tissue membranes. The abdominal cavity is lined by the peritoneum lines.
Several fluid-filled anatomical compartments in body.
- Blood-filled vessels/heart of circulatory system
- Eyes: hollow fluid-filled spheres subdivided into 2 compartments: aqueous and
vitreous humors
- Cerebrospinal fluid (CSF) around brain and spinal cord.
- Membranous sac that surrounds heart (pericardial) and lungs (pleural)
contains small volumes of fluid.
The interior of any hollow organ (heart, lungs) is called the lumen. It can consist of
fluid or air (bv. Lumen of blood vessels filled with blood)
For some organs like intestine, lumen is extension of external environment and not
part of body’s internal environment until it crosses wall of organ.
,Most cells in the body are not in direct contact with the outside world, instead their
external environment is in contact with extracellular fluid (ECF). We can divide the
body in two main fluid departments:
ECF: outside of the cells
ICF: the inside of the cell
ECF and ICF are divided by cell membrane.
The ECF subdivides further into:
- blood plasma (fluid portion of the blood, extracellular fluid inside blood
vessels)
- interstitial fluid (which surrounds most cells of the body).
A membrane is described as a tissue that lines a cavity or separates two cavities.
We have the mucous membranes in the mouth and vagina, the peritoneal membrane
that lines the inside of the abdomen, the pleural membrane that covers the lungs and
the pericardial membrane that surrounds the heart. These membranes are tissues:
thin, translucent layers of cells.
Cells also have membranes: a bilayer of phospholipid membrane that separates
the aqueous fluids of the interior and the outside environment.
So membrane can apply to a tissue or to a phospholipid-protein boundary layer.
Lipid bilayer consists of cholesterol + phospholipids
The general functions of the cell membrane/=plasma membrane/=plasmalemma:
Physical isolation; separates intracellular fluid from surrounding extracellular
fluid
Regulation of exchange with the environment. Controls entry of
ions/nutrients inside cell, eliminates cellular waste, release products from cell.
Communication between the cell and its environment. Cell membrane
contains proteins that recognise/respond to molecules/changes in external
environment, alterations in cell membrane affect cell’s activity.
Structure support proteins in the membrane hold the cytoskeleton as well as
the junctions and the extracellular matrix (=extracellular material that is
synthesized and secreted by cells), cell-cell and cell-matrix junctions stabilize
the structures of tissues.
Secretion= process by which a cell releases substance into extracellular
space.
All biological membranes consist of a lipid and protein + small amount of
carbohydrate.
Ratio of lipid-protein varies in different membranes.
- The more metabolically active a membrane is the more proteins it contains bv.
Inner membrane of mitochondrion that contains enzymes for ATP production
contains ¾ protein.
Fluid mosaic model of membrane
, Lipids of biological membrane are mostly phospholipids arranged in bilayer, so
phosphate heads are on membrane surface and lipid tails are hidden in center of
membrane. Cell membrane is studded with protein molecules and extracellular
surface has glycoproteins/glycolipids.
3 main types of lipids make up cell membrane:
- Phospholipids; made of glycerol backbone with 2 fatty acid chains extending
to one side and phosphate group extending to other site.
- Sphingolipids
- Cholesterol; are mostly hydrophobic, insert themselves between hydrophilic
heads of phospholipids. Helps to make membrane impermeable to small
water-soluble molecules and keeps membrane flexible over wide range of
temp.
The glycerol phosphate head is polar and thus hydrophilic. Fatty acid tail is nonpolar
so hydrophobic. lipids of biological membranes are mostly phospholipids arranged in
a bilayer so that the phosphate heads are on the membrane surfaces and the lipid
tails are hidden in the centre of the membrane. It is studded with protein molecules.
The arrangement of the membrane can in three structures:
The micelles are the small droplets with a single layer of phospholipids
arranged so that the interior of the micelle which is filled with the hydrophobic
fatty acid tails (important in digestion and absorption of fat in digestive tract)
Liposomes: larger spheres with bilayer phospholipid walls. Leaves a hollow
centre with watery core that can be filled with water soluble molecules can
be filled with drugs/ or fragments of DNA for gene therapy, to make drug
delivery more specific: immunoliposomes use antibodies to recognize specific
types of cancer cells)
Sphingolipids (phospholipid): have fatty acid tail, but heads are either
phospholipids or glycolipids. Sphingolipids are slightly longer than
phospholipids.
The 4 components of cell membranes:
Cholesterol barrier
Phospholipids barrier
Carbohydrates structural stability, cell recognition, immune response
Proteins structural stability, cell recognition, immune response
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