topic six Flashcards
human digestive system
amylase
digests starch
peristalss
a wave of contraction and relaxation of the longitudinal and circular muscles of the alimentary canal, by which the contents are forced along the tube.
when is the mixture of food mixed with acd in the stomach
chyme
purpose of the stomach acid
kills bacteria and starts the digestion of proteins
first part of the small intestine
duodenum
second part of the small intestine
ileum
what happens in the small intestine
the acid passing from the stomach needs to be neutralised so that enzymes in the small intestine can function properly. These enzymes have an optimum pH of neutral to alkaline, and some of them digest fats and lipids: others further digest carbohydrates; and others further digest proteins. By the time your food reaches the end of the small intestine, digestion has been completed and the digested products have been absorbed from the last section, the ileum. The small intestine is where most of the absorption takes place.
what does the pancreas secrete
amylase, lipase and proteasae
what does the liver secrete
bile to emulsify lipids
what stores bile
gall bladder
structure of the small intestine
a muscular tube of about 6–7 m in humans that lies between the stomach and the large intestine. It can be divided into three parts, namely the duodenum, jejunum and ileum. The inner surface of the small intestine is covered with specialised structures called villi (singular: villus), which increase its surface area by 30–60 fold: this increase in surface area is essential for absorption, which will be discussed later.
If you go from outside of the tube towards the inside, you will come across the following tissue layers:
serosa
longitudinal muscles
circular muscles
submucosa
mucosa
serosa
the outermost layer consisting of connective tissue that is in contact with body cavities.
longitudinal and circular muscles
responsible for peristalsis
submucosa
connective tissue that supports the mucosa and that contains large veins and arteries which give rise to the capillary bed of the mucosa.
mucosa
innermost layer forming the soft lining of the tube comprised of epithelium (which lines the lumen of the digestive track), connective tissue and smooth muscle (villi form part of this layer).
endopeptidase
breaks down proteins into smaller polypeptides
lipases and phospholipases
break down lipids and phospholipids respectively, to glycerol and fatty acids. In the case of the phospholipid, phosphate is also produced.
nucleases
break down dna and rna
maltase
breaks down maltose into glucose
lactase
breaks down lactose into galactose and glucose
exopeptidases
remove a single AA from the end of the small polypeptides
dipeptidases
break down a dipeptide into two amino acids
what are the villi
location of absorptionof all the monomers p-roduced by the digestive processes in the small intestine
label a villus
abosprtion is
the taking in of dgested food substances as well as minerals and vitamins from the lumen of the small intestine into the blood
what produces mucus in the small intestine
goblet cells
what carries nutrients and vitamins away from the villus
capilary network and lacteal
what is the lamina propria
connective tissue of the villus
The following molecules, which are the end products of digestion, are directly absorbed by the villi:
Bases and phosphates from nucleic acids
Fatty acids and glycerol
Amino acids
Monomeric carbohydrates, such as fructose, glucose, galactose and ribose.
which organs job is detoxifying contimaniants or poisons
the liver
where are fats absorbed
into the lymph which which circulates in the lacteal in the centre of the villus
where are food molecules, minerals and vitamins absorbed
into the blood or the lymph. To be absorbed into the blood, the molecules need to pass into the capillaries of the villus.
Two-step absorption from the lumen of the small intestine into
capillaries and lacteals of a villus.
- Substances to be absorbed move from the lumen into the epithelial villi.
- Amino acids and monosaccharides move from the villi into the capillaries and monoglycerides move into the lacteals.
when does simple diffusion occur in food absorption
Occurs when molecules are small and are hydrophobic (so they can pass through the phospholipid bilayers). This occurs mostly with the products of lipid digestion.
when does facilitated diffusion happen in food absorption
Fructose, glucose and other hydrophilic monomers are moved by protein channels. Be aware, this still requires a concentration gradient.
when does active transport happen in food absorption
s needed when the concentrations are lower in the lumen of the small intestine. Thus, the movement needs to occur against a concentration gradient. Glucose, amino acids and some mineral ions are transported out of the lumen in this way, which requires ATP. The cells of the epithelium have many mitochondria that can synthesise ATP for this process.
when does pinocytosis happen in food absorption
Draws in small droplets of liquid surrounded by a small section of the phospholipid membrane, as shown in Figure 2. This is most likely to occur with fat droplets in the lumen of the small intestine.
The absorption of fats differs from that of carbohydrates because:
Most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood.
why must glucose be absrobed by facilitated diffusion and active transport
Glucose is a large hydrophilic molecule, therefore it cannot pass through the phospholipid bilayer. The only way it can cross the cell membrane is by passing through a protein as would occur during facilitated diffusion and active transport.
describe the absorption of nutrients from the lumen of the small intestine to the capillaries?
Nutrients move from the lumen of the small intestine, across the plasma membrane of the epithelial cell; move across the epithelial cell; then cross the plasma membrane on the other side of the cell. The nutrients then move out of the epithelial cell and into the capillary.
two different forms of starch
amylopectin (branched)
amylose (linear)
what does amylase break down specifically
the α-1,4 glycosidic bonds that connect the glucose monomers in amylose and amylopectin
end products after amylase digests starch
maltose, a dimer of glucose connected by α-1,4 bonds, and maltotriose, which is comprised of three glucose molecules also connected by α-1,4 bonds
what other bond does amylopectin contain
α-1,6 glycosidic bonds, however, these cannot be broken down by amylase.
what is the branching of amylopectin caused by
α-1,6 glycosidic bonds
The molecular structure of amylose.
Even after the initial catalytic breakdown by amylase, the di- and tri-saccharides produced from the starch molecules are too large to pass through membranes, so
they need to be broken down into monomers (monosaccharides) before they can be absorbed.
what parts of starch enter the small intestine
a mixture of maltose, maltotriose and dextrins
what are dextrins
very small polymers still containing the α-1,6 glycosidic bond.
which enzymes are immbolised in the epithelial cells of the small intestine
maltase, glucosidase and dextrinase
All absorbed monomers from food are transported via
the hepatic portal vein from the small intestine to the liver, from there it enters the general circulation.
absorbed food (including glucose formed from the breakdown of starch) is first transported by blood to the WHERE before being distributed to the whole body.
liver
what is visking tubing
partially permeable cellulose tubing that contains microscopic pores
It allows water, small molecules and ions to pass through freely, but does not allow the movement of large molecules.
what is dialysis
the separation of smaller molecules from larger molecules in solution by selective diffusion through a partially permeable (also known as selectively permeable or semipermeable) membrane.
waht does the visking tubing represent
the epithelium fo the small intestine
the movement of glucose mimics the
absorption of glucose via the epithelial cells, in this case, represented by the dialysis tubing, into the blood supply.
shortcoming of the visking tubing model of digestion
it can only account for absorption by diffusion or osmosis, and cannot be used to model absorption by active transport.
When the heart pumps blood into the aorta, the main and biggest artery connecting the heart with the rest of the body, it exerts a systolic pressure of between
120 and 200 mm Hg
waht does systolic reger to
the part of the heartbeat when the muscle is contracting
what does diastolic refer to
When cardiac muscle is relaxing, that part of the heartbeat is called the diastolic portion
is diastolic or systolic pressure lower
diastolic
two numbers of blood pressure
systole / diastole
artery walls can cope with high pressure because
The walls contain elastic fibres formed from elastin protein, which are stretched at every heartbeat when the pressure is highest. When the walls return to their normal shape, this recoil helps to propel the blood forward. Arteries also have muscular walls to help with the propulsion of the blood. Overall, the muscle and elastic fibres present in the wall of the arteries assist in maintaining blood pressure between pump cycles.
the role of the arterial muscle is to keep
arteries narrow enough to maintain the high pressure needed to ensure that the blood has the speed and pressure needed to reach all parts of the body.
layers of the artery walls
tunica intima
tunica media
tunica adventitia / externa
the part of the tunica intimia facing the lumen is lined with
the endothelium
tunica intima
This is the innermost layer and is in direct contact with the blood in the lumen. It includes the endothelium that lines the lumen of all vessels; thus forming a smooth, friction-reducing lining.
tunica media
This is also known as the middle coat and is mainly made up of smooth (involuntary) muscle cells and elastic fibres arranged in roughly spiral layers. This layer is usually the thickest of the three layers.
tunica adventitia
This is also known as the outermost coat and is a tough layer consisting largely of loosely woven collagen fibres that protect the blood vessel and anchor it to surrounding structures.
the highest pressure
is systolic
what happens in the circular muscles during systolic blodo pressure
The circular muscles surrounding the arteries resist the outward pressure and constrict. This is called vasoconstriction.
what happens in the circular and longitudinal muscles during diastolic blood pressure
When the heart relaxes between beats, the pressure in the arteries is lowest: diastolic blood pressure. The smooth muscles surrounding the arteries can also relax, and this called vasodilation
smaller arteries branch off in the bdy to supply blood to organs, limbs called
arterioles
aterioles have
a higher density of muscle and are more susceptible to the hormonal and nervous control of vasoconstriction and vasodilation
stroke volume
the volume of blood pumped out of the left ventricle of the heart during each contraction (or heartbeat).
caridac output
the volume of blood the heart pumps through the circulatory system in a minute.
Muscle fibers and elastic fibers are essential to the function of arteries. Which of the following layers contains these fibers?
The tunica adventitia
The endothelium
The tunica intima
The tunica media
tunica media
how is blood flow moderated in veins
skeletal muscles: When you move around, especially during vigorous exercise, the muscles squeeze the veins like a pump.
valves to prevent backflow
when do valves open and close
composition of blood
plasma, rbc, wbc, platelets
what does plasma carry
proteins
hormones
co2
glucose
vitamins and minerals
waht do rbc contain
hemoglobin
what do wbc do
part of theimmune system, defend from disease
waht do platelets do
involved in the mechanisms that clot blood when blood vessels break
the connection betwen arteries anveins is formed by a
capillary network
why is a cap network needed
The nutrients and oxygen in blood need to reach each and every cell of the body. However, the size and wall structure of arteries is too big for that purpose. Arteries cannot fit between individual cells if they are large, and they cannot allow for efficient diffusion if there are many cells through which substances must diffuse. Thus, the arteries divide to form smaller arterioles that in turn divide successively to form very fine blood vessels called capillaries. These vessels then fuse together to form venules, and many venules fuse together to form veins
how thick are cap walls
one cell thick with a diamter of around 3-4 µm
benefit of cap wall being leaky
allows exchange of materials, oxygen and nutrients with cells in tissues and waste products, such as co2 and urea, back into the capillaries to be transproted by blood. wbc can also exit through gaps between endothelial cells
The liquid part of blood that passes through the capillary wall, to bathe tissue cells is known as
tissue fluid or interstitial fluid
what composes the tissue fluid or interstitial fluid
water, sugars, salts, fatty acids, amino acids, coenzymes and hormones, as well as waste products from the cells. Since tissue fluid containing dissolved nutrients is in direct contact with tissue cells, exchange of materials between cells and fluid, which occurs by diffusion or active transport, is greatly enhanced. After the exchange has taken place, tissue fluid is mostly reabsorbed into capillaries, which ultimately drains into venules
What is present in all arterioles that is not present in all capillaries?
Circular smooth muscle cells
What is the function of the gaps between the endothelial cells of capillaries?
Permitting exchange of materials between the blood and the tissue cells
diagram of the heart
what are The tricuspid valve and the bicuspid valves are sometimes called
the right and left atrioventricular valves.
how does blood flow through the body
Right side of the heart
Blood enters the heart through the inferior and superior vena cava, with oxygen-poor blood from the body tissues flowing into the right atrium of the heart.
As the atrium contracts, blood flows from the right atrium into the right ventricle through the open tricuspid valve.
When the ventricle is full, it begins to contract. The increased pressure of blood against the tricuspid valve forces it shut. This prevents blood from flowing backwards into the atrium.
As the ventricle contracts, blood leaves the heart through the pulmonary valve, into the pulmonary artery and flows to the lungs where it is oxygenated.
Left side of the heart
The pulmonary vein carries oxygen-rich blood from the lungs into the left atrium of the heart.
As the atrium contracts, blood flows from the left atrium into the left ventricle, through the open bicuspid (also called mitral) valve.
When the ventricle is full, it begins to contract. The increased pressure of blood against the bicuspid valve causes it to close. This prevents blood from flowing backward into the atrium while the ventricle contracts.
As the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta and to the body.
Which of these options correctly describes the location and function of the tricuspid valve?
Ensure the one-way flow of deoxygenated blood from the right atrium to the right ventricle.
what does the heart being myogenic mea
the heart muscle can generate its own contractions
what initiates the heartbeat
the sinoatrial node
regular bpm
60-70
points essential in heart contraction
The propagation through the heart of the electrical signal initiated in the SA node can be summarised as follows:
The SA node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria.
The signal then passes via interatrial septum to reach the atrioventricular (AV) node.
From the AV node, the signal is relayed via the bundle of His located in the interventricular septum to the top of each ventricle (confusingly, the top of the heart, or apex, is the bottom-most part where the two ventricles meet in a shape somewhat like a point).
At the top of the ventricles, the signal spreads from the bundle of His (also called the atrioventricular (AV) bundle), to the ventricles via the Purkinje fibres located in its wall.
what is the cardiac cycle
refers to the complete sequence of events in the heart from the start of one beat to the beginning of the following beat.
pressure and volume change in the cardiac cycle
cardiac cycle
- Atrial contraction begins ( atrial systole) .
- Atria eject blood into ventricles ( atrial systole) .
- Atrial systole ends; AV valves close (‘lubb’ sound).
- Isovolumetric contraction of the ventricles occurs ( ventricular systole) .
- Ventricular ejection occurs.
- Semilunar valves close (‘dupp’ sound).
- Isovolumetric relaxation of the ventricles occurs ( ventricular diastole) .
- AV valves open; passive ventricular filling occurs.
Isovolumetric contraction is a term used to refer to
an event occurring at the beginning of systole, during which the ventricles contract with no corresponding volume change. This can occur because the valves are closed. This type of contraction makes the pressure in the heart chamber rise so that the blood can be forced out of the ventricle into the artery in a one-way direction.
provide the correct sequence of events for the propagation of the electrical signals initiated in the SA node to the ventricles?
SA node → AV node → Bundle of His → Purkinje fibres → Walls of the ventricles
what can signal the SA node to speed up the heart or slow it down
the cardiac accelerator nerve / vagus nervw
what monitors blood pressure, pH and co2
cardiovascular centre
aaside from changes in blood pressure, pH and co2 that is detected by the cv centre, what is another factor that influences the SA node
epinephrine/adrenaline
Epinephrine increases the heart rate by
stimulating the SA node to emit electrical signals at a faster rate as well as by increasing the conduction speed of impulses generated by both the SA and AV nodes.
Cross section of the human skin.
Antibody production by B lymphocytes
label an antibody
Gas exchange in an alveolus.
inspiration
expiration
Muscles involved in inspiration and expiration.
Propagation of a nerve signal
Conditions that affect the level of leptin production and action on the body
female reproduction system
female repdocution system front
Male reproductive system side view
Male reproductive system front view.
he menstrual cycle. The letters a–d refer to the explanations below.
steps in IVF
Step 1a: The woman is given a drug (or drugs) to suppress her natural cycle by suspending her normal secretion of hormones. She can administer them herself in the form of a daily injection or a nasal spray. The drug treatment continues for about 2 weeks.
Step 1b: FSH and LH are injected at a higher dose than normal for around 12 days to stimulate the production of a number of ova (egg cells), called superovulation. The clinic monitors progress throughout the drug treatment through vaginal ultrasound scans and, possibly, blood tests.
Step 2: Between 34 and 38 hours before the eggs are due to be collected, the woman will be given a hormone injection to help the eggs mature (this is likely to be human chorionic gonadotrophin). Eggs are then usually collected from the ovaries by using ultrasound guidance while the person is sedated. A hollow needle is attached to the ultrasound probe and is used to collect the eggs from the follicles in each ovary.
Step 3: A sperm sample is collected from the woman’s partner and checked for viability.
Step 4: The eggs are mixed with the partner’s or the donor’s sperm and cultured in the laboratory for 16–20 hours after which they are checked for signs of fertilisation. (Sperm can also be injected directly into the egg, as shown in the alternate picture on the right at number 4 in the diagram.) Eggs that are fertilised (now called embryos) are grown in the laboratory incubator for up to 6 days. The embryologist will monitor the development of the embryos and the best will then be chosen for transfer. The remaining embryos of suitable quality are frozen for future use.
Step 5: If the woman is under the age of 40, one or two embryos are implanted in the uterus at the appropriate time in her menstrual cycle. But, if she is older than 40 years, a maximum of three may be used. The number of embryos transferred is restricted because of the risks associated with multiple births.
