Foundations of Medicine Block 1 Week 1 Flashcards
How many cells are there in the body ?
37 trillion cells in the body
What is another name for the colon ?
Large Intestine
What are the main layer of the large intestine wall ( from inner to outer)?
Mucosa (Most inner layer)
Submucosa
Muscularis propria
Subserosa
Serosa (outer layer)
What is the Mucosa layer of the wall of the large intestine made up of ?
Mucosa:
Epithelium
Connective Tissue
Thin muscle layer
What cells line the wall of the large intestine ?
Simple columnar epithelium
The intestinal villi are covered by two types of cell. What are these two types of cell ?
- Goblet cells - These are simple columnar epithelium cells whose sole function is to secrete mucin, whcih dissolves in water to from mucus.
2.Intestinal Absorptive cells - called Enterocyte
These are simple columnar epithelium cells.
Absorb molecules from the lumen including proteins, fats, sugars, water, electrolytes, vitamins and bile salts.
What are the functions of a cell?
- Division
- Differentiation
- Migration
- Adhesion
- Secretion
- absorption
- degradation
- sensing
- signaling
- survival
- death
What is a nucleus ?
Contains genetic information
Controls gene expression
Directs cells activities
What is an endoplasmic reticulum ?
Two types:
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Function:
Ribosomes are found on the rough endoplasmic reticulum
System for protein synthesis
Smooth Endoplasmic Reticulum (SER) function:
Synthesize steroid hormones from cholesterol
Manufactures carbohydrates and lipids
What is the Golgi apparatus ?
Stores and transports proteins
Transporting, modifying and packaging proteins and lipids into vesicles for delivery to targeted destinations
Lysosome enzymes are made by proteins from the endoplasmic reticulum and enclosed within vesicles by the Golgi apparatus.
Golgi apparatus form secretory vesicles which that migrate to the plasma membrane.
What are ribosomes ?
Ribosomes consist of proteins and ribonucleic acid (RNA)
They are formed in the nucleus and migrate to the cytoplasm .
Ribosomes function is to make new proteins
Some ribosomes become attached to the outer membrane of the endoplasmic reticulum to form the RER.
What is the Cytoskeleton ?
Cytoplasm and cytoskeleton are two components of a cell.
Cytoplasm is a fluid composed of cytosol , organelles, CYTOSKELTON and inclusions.
Cytoskeleton is composed:
Microtubules - play an important role in moving organelles
Intermediate Filaments - role in mechanical stability of cells
Actin Filaments - These play an important role in cell movement., such as the contraction of skeletal muscle.
They also help to keep cell shape in non-motile cells
What are Mitochondria ?
Oxidize glucose and fats to provide energy for other activities such as motility, synthesis of proteins, growth and repair.
The energy is provided by ATP.
The process of called ATP synthesis is called Oxidative Phosphorylation.
This takes place on the inner membrane of the mitochondria in a process known as tricarboxylic acid cycle and electron transport chain.
What is the function of the endocytic network ?
Take up and digestion
What are endosomes?
A vesicle formed by the invagination and pinching off of the cell membrane during endocytosis.
Endocytic pathway ?
Size at which we can see mitochondria using a microscope ?
2 micrometres
Describe the two main types of light microscopy ?
Bright - field light microscopy:
Used to image fluids and tissues samples
Often rely on dense stains incompatible with living cells
Fluorescence light microscopy:
Use a much higher intensity light to illuminate the sample.
Greater sensitivity : specify achievable (e.g. antibodies)
giving more precise localization (molecular level).
What is electron microscopy and describe the two main types ?
Electron microscopy (EM) is a technique for obtaining high resolution images of biological and non-biological specimens
As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a higher resolving power than light microscopes and can reveal the structure of smaller objects
SEM - 10,000,000 x magnification
Light Microscope - 2000 x Magnification
TEM;
Beam of electrons is transmitted through the specimen to form an image
Requires a very thin specimen
SEM: is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample.
Where does transcription from DNA to RNA occur?
Nucleus
What is Electron tomography ? (ET)
Detailed 3D structures of sub-cellular macro-molecular objects
Electron tomography is an extension of traditional transmission electron microscopy and uses a transmission electron microscope to collect the data.
Serial TEM collected data:
thousand of images from a sample taken at different depths/ angles and computer analysis reconstituting a static 3D view.
Exocytosis occurs by three pathways what are they ?
Constitutive and regulated
Lysosomes
Why do we need exocytosis and endocytosis ?
Polar molecules cannot penetrate through the lipid barrier of the cell membrane.
Polar molecules (such as digestive enzymes) are packaged in membrane-bound vescicels that can fuse
Why do we need exocytosis and endocytosis ?
Polar molecules cannot penetrate through the lipid barrier of the cell membrane.
Polar molecules (such as digestive enzymes) are packaged in membrane-bound vesicles that can fuse with the plasma membrane to release their contents into the extracellular space- this is known as exocytosis
What are the three exocytosis pathways ?
1.Constitutive exocytosis
2. Regulated exocytosis
3. Lysosome mediated exocytosis
Basic process of exocytosis:
Vesicles containing molecules are transported from within the cell to the cell membrane.
The vesicle membrane attaches to the cell membrane.
Fusion of the vesicle membrane with the cell membrane releases the vesicle contents outside the cell.
Constitutive: involves regular secretion of molecules. This action is performed by all cells.
Regulated: relies on the presence of extracellular signals for the expulsion of materials within the vesicles.
Does not occur in all cells. Mainly only secretory cells.
Secretory cells store products such as hormones, neurotransmitters and digestive enzymes that are released when triggered by extracellular signals.
Lysosomes: Carry digested material to the cell membrane where they fuse with the membrane and release their content into the extracellular matrix.
What are the 4 pathways of endocytosis ?
1.receptor-mediated endocytosis (also known as clathrin-mediated endocytosis) - takes in most things. There are 20 receptors which works this way.
2. caveolae - take in nanoparticles.Particles usually 50-100 nanometres.
3. pinocytosis - take in fluid with dissolved small molecules.
4. phagocytosis - part of the immune system. Ingest particles larger than 50 micrometres into a phagosome.
What is endocytosis ?
Endocytosis is used by cells to retrieve components of the plasma membrane and to take up macromolecules from the extracellular space.
What is phagocytosis ?
Phagocytosis is a specialized form of endocytosis in which large particles (e.g. bacteria or cell debris) are ingested by phagocytes.
The pri
What are peroxisomes?
Peroxisomes are small membrane enclosed organelles that contain enzymes (at least 50 different enzymes) involved in a variety of metabolic reactions, including several aspects of energy metabolism.
Site of oxidative reactions with hydrogen peroxide production.
Hydrogen Peroxide is then converted into water and oxygen.
Another site of fatty acid metabolism.
What are the 3 ways cells communicate with each other ?
- By diffusible chemical signals - allows cells to communicate at a distance
- By direct contact between the plasma membrane of adjacent cells - important in cell-cell recognition during development.
- By direct cytoplasmic contact via gap junctions - permits the electrical coupling of cells and plays an important role in the spread of excitation between adjacent cardiac muscle cells.
In which 3 ways to cells use diffusible chemical signals ?
- Paracrine signaling - when the secreted signal acts on cells nearby (local). The signaling molecules are destroyed rapidly by extracellular enzymes or by uptake into the target cells. Consequently very little of the secreted material enters the blood.
- Endocrine signaling - Hormones are secreted into the blood by endocrine glands, to act on various tissues around the body. (not localized). Because hormones are circulated their actions are often slow and long-lasting ( ranging from seconds to hours)
- Synaptic Signaling - Nerve cells release chemicals at their endings to affect the cells they contact.
Give two examples of Paracrine signaling ?
- Prostaglandins secreted by a cell act on neighboring cells to stimulate them to produce more prostaglandins.
2.Mast cells in tissues have secretory granules which release histamine. Histamine dilates local arteriole and increases the permeability of local nearby capillaries.
Endocrine glands secrete hormones in response to a variety of signals. Give 3 examples of these?
- They may respond to chemical level in the blood. E.g. Insulin secretion from the B -cells of the pancreatic islets is regulated by the blood glucose concentration.
- They may respond to the level of other hormones in the blood. E.g. Sex hormones from the ovaries ( estrogen) and testes (testosterone) which are secreted in response to hormonal signals from the anterior pituitary gland.
- They may respond to the activity of nerves - this is how oxytocin secretion from the posterior pituitary gland and prolactin secretion by the anterior pituitary gland are controlled during lactation.
Which structure which releases hormones is an exception in the endocrine signaling pathway?
The releasing hormones of the hypothalamus. These hormones are released into portal blood vessels and travel to the anterior pituitary gland where they control the secretion of the anterior pituitary hormones.