Human and Animal Physiology Flashcards
State the definition of nutrition
Nutrition is the process by which an organism acquires the matter and energy it requires from the environment.
List the types of nutrition
- Heterotrophic nutrition - animals obtain matter and energy from other organisms.
- saprotrophic nutrition - feeding on the
dead matter
- parasitic nutrition - feeding on the host’s
tissues.
- holozoic nutrition- the ingestion of liquid
and solid material from the bodies of other
organisms. - Autotrophic nutrition- the green plants synthesize their organic molecules from the inorganic substances through photosynthesis.
State the five steps of nutrition
- Ingestion- food is taken into the mouth for processing in the gut.
- Digestion - we include mechanical digestion (action of teeth and muscular walls of the gut) and chemical digestion (by the enzymes).
- Absorption - the process of the digested products being absorbed into the bloodstream.
- Assimilation - products of digestion absorbed in the blood stream are then transported to body tissues.
- Egestion - removal of the undigested food, bacteria as the feces from the body.
What is the role of digestion in the nutrition?
Digestion helps in the processing and breaking down the large molecules into smaller ones that can’t enter the blood system.
What is the mechanical digestion?
Mechanical digestion includes the action of chewing food by teeth, to break the ingested food into smaller pieces that are more readily digested by the chemical digestion.
Explain the peristalsis movement
Peristalsis can be defined as the involuntary muscle movement of food through the gastrointestinal tract. Therefore, it helps to move the food to the stomach where it can go through chemical digestion.
Chemical digestion
Chemical digestion is the breakdown of the large molecules into small molecules through the enzyme activity and hydrolysis. It breaks down complex molecules such as fats, proteins, and carbohydrates.
State the human digestive enzymes
- Amylase - it is the carbohydrate macromolecule. Example: salivary amylase (mouth).
- Protease - protein macromolecule. Example trypsin (duodenum).
- Lipase - lipid macromolecule. Example: Pancreatic lipase (pancreas).
How the digestion looks like in the carbohydrates?
Food reaches the mouth and salivary amylase breaks down the disaccharides and starch. Then it is broken down in the pancreas by the pancreatic amylase. In small intestine the disaccharides are broken down into lactose, maltose, and sucrose.
Explain the digestion of lipids
They are ingested as large masses and digested within the duodenum by the pancreatic lipase. This enzyme breaks down the large molecules into smaller droplets. It increases the surface area of fat which increases the rate of lipid digestion.
How the digestion of proteins looks like?
Digestion in proteins occurs as the endopeptidases break down the peptide bonds of the proteins (large proteins - small proteins). Exopeptidases remove the amino acids that will be needed for absorption.
What are the structures specialized for the digestion and absorption of food (10)?
- Mouth
- Trachea
- Oesophagus
- Liver
- Gall bladder and bile duct
- Stomach
- Pancreas
- Small intestine (duodenum, jejunum, ileum)
- Large intestine (colon, rectum)
- Anus
What happens in the mouth?
- chewing (mechanical digestion)
- salivary amylase begins the chemical
digestion of starch
What happens in the oesophagus?
- peristalsis pushes the food into the
stomach
What happens in the stomach?
- gastric pits release the gastric acid and
enzymes - the hydrochloric acid lowers the pH and
kills the bacteria - pepsin enzyme starts protein digestion
and stretches receptors in the muscular
wall to trigger the release of enzymes
Digestion in the small intestine
Duodenum: chyme enters the duodenum and the liver is emptied into it. Bile from the liver and gall bladder neutralizes the acid. Pancreatic amylase and lipase digest carbohydrates and fats. Trypsin digests polypeptides to amino acids.
Ileum: lower half of the small intestine absorbs nutrients into the blood via the villi.
Digestion in the large intestine
Water and mineral salts are reclaimed and returned to the blood. It leaves the feces which is stored in the rectum.
What happens in the anus?
The undigested food, dead cells, and other water is forced out of the anus and released out of the human body.
Define the function of lumen
It stores the food when it reaches the stomach space.
What are the components of the gastric juice?
- hydrochloric acid
- protease enzymes - break down the proteins into short chains of amino acids
- goblet cells - secrete mucus
- Mucus - prevents the destruction of stomach wall (autolysis)
The function of villi
It increases the surface area for absorption and have a rich blood supply.
How absorption works in the small intestine?
It is the uptake into the body of the useful products of digestion. It is efficient because intestine has a huge surface area, due to large number of villi.
What is the structure of the ileum?
- Villi - contains epithelial cells joined with tight junctions and microvilli which increase the surface area.
- Mucosa - secretes mucus
- Submucosa - contains secretory cells
- Muscles - generate peristalsis
How the absorption of the glucose works?
Absorption through the epithelium and this transport is called a sodium-glucose symporter. The protein binds to glucose and Na+. This mechanism is optimizing the glucose absorption. Coupling with the NA+ permits getting glucose out of the lumen. Then glucose is absorbed to the bloodstream by facilitated diffusion.
Explain assimilation
Uptake of nutrients into cells and tissues from the bloodstream (after absorption). Absorbed nutrients are transported from intestine and then they are moved to the liver. The enzymes also pass into the capillary network and then to the liver. New proteins in the liver are made.
Function of the liver
It secretes biles and helps in maintaining homeostasis by removing or adding nutrients to the blood. Regulates the quantity of nutrients circulating in the blood. It also converts excess glucose to glycogen and then stores it.
What are the exocrine glands?
They release their sections into ducts. We include the:
- goblet cells in the small intestine
- pyloric glands in the stomach
- salivary glands in the mouth
What are some of the contents of saliva (4)?
- amylase for starch digestion
- lipase for digestion of fats
- water for moistening
- antibacterial compounds
Where is the gastric juice produced and what it contains?
In parietal cells in the stomach wall. It contains the HCL, mucus and enzymes such as pepsin.
What pancreatic juice contains?
- pancreatic lipase
- pancreatic amylase
- trypsin
What are inactive precursors?
If pepsin and trypsin were secreted as active enzymes they would cause damage to exocrine glands (autodigestion). They are instead secreted as inactive precursors, that become activated under the right conditions so they do not cause any damage.
Explain the enterokinase
Enzyme produced by cells of the duodenum. It helps the food from the stomach to enter the intestine.
How the proton pump inhibitors work?
- drugs that irreversibly bind to the proton pumps and prevent the H+ secretion
- they raise the pH in the stomach to prevent the discomfort caused by gastric juice.
Normal proton pumps
- secrete H+ ions which combine with Cl- ions to form hydrochloric acid
- lower the pH in the stomach (kills the bacteria)
How the gastric juice secretion is controlled (exam question)?
- Reflex response to visual and smell stimulus leads to release of the gastric juice.
- As the food arrives in the stomach, it triggers the release of gastrin in the stomach walls. This hormone stimulates the production of gastric juices.
- Chyme passes from the stomach to the duodenum. Duodenum releases the CCK and secretin hormones. CCK stimulates the release of digestive enzymes from the pancreases and of the bile from gallbladder. Secretin stimulates the pancreas to neutralize the chyme.
- However, if the chyme is rich in fats, the high levels of secretin and CCK act on stomach to inhibit peristalsis and secretion of gastric juices, which slows down the digestion process.
State the definition of chyme
An acidic mixture of partially digested food
Pre-ingestion meaning
The sight and smell of food triggers an immediate response by which gastric juice is secreted by the stomach.
How the pre-ingestion works and how it leads to digestion?
Smell and sight receptors send signals to brain, which triggers the secretion of gastric juice. Stomach releases gastrin, which promotes the production of the stomach acids. Whereas, the pancreas releases secretin and CCK. It stimulates the secretion of the pancreatic juice and bile.
What is the cholera toxin?
Cholera is the infection that increases the adenylate cyclase activity which increases the cAMP action. It leads to release of excess concentrations of water and therefore that causes the diarrhea.
What are the epithelial cells?
They are adapted to maximize absorption of digested food molecules in the ileum.
Function of microvilli
Maximize the surface area for absorption
Function of tight junction
Prevent the movement of molecules between the neighboring cells.
Function of mitochondria in digestion
Provides the ATP for the active transport of digested food molecules.
How the processing of food works in the large intestine?
The colon reabsorbs water. The undigested material contains the fiber called the cellulose fiber. This fiber helps to move food along the alimentary canal. Then the undigested food is released from the anus.
How blood vessels carry the blood?
The blood is carried through the body via the blood vessels. The artery carries blood away from the heart, where it branches into arterioles which branch into capillaries. Capillaries combine with other vessels to form venules. They carry blood into the vein, which returns the blood to the heart.
Pulmonary circuit
In this circuit arteries carry blood low in the oxygen to the lungs for gas exchange. Pulmonary veins return freshly oxygenated blood from the lungs to the heart, which is pumped into the systematic circulation.
Systemic circuit
Organs are supplied with blood by the artery branching from the main aorta. The artery branches into arterioles and the smallest arterioles supply the capillary network. Capillaries drain to venules and venules join to form veins. The veins join the vena cava carrying blood back to the right side of the heart.
Explain the blood supply in the liver
The liver has the double supply of the blood. It receives the oxygenated blood via the hepatic artery, which sustains the liver cells. It also receives the nutrient-rich blood from the gut via the portal vein. Oxygenated blood is transported from the liver via the hepatic vein which is transported to the lungs.
Liver structure
- vena cava
- right lobe of the liver
- right hepatic duct
- bile duct
- gallbladder
- hepatic portal vein
What is the portal triad in the liver?
The structure that contains bile duct, hepatic artery and hepatic vein.
- hepatic artery - oxygen blood
- hepatic portal vein - nutrient rich blood
Explain the sinusoids
Small, wide blood vessels found in the liver. They have the surrounding basement membrane which is incomplete and endothelial layer that contains large gaps.
Function of Kupffer cells
Break down erythrocytes
Role of the liver in the regulation of nutrient levels in the blood
- the liver stabilizes blood glucose levels
- if they drop, the hepatocytes break down the glycogen and release glucose into the bloodstream
- they also synthesize glucose from other compounds -> glucogenesis
- if the blood climb - hepatocytes remove glucose from the bloodstream
- then liver stores it and synthesizes lipids
Explain the concept of the bile
Bile is the structure that is produced by hepatocytes. It is carried in the large ducts to the gallbladder, where it is stored.
Explain the function of the bile
- Its acids break down fat globules and those fats are emulsified into small droplets.
- It is important for the transport and absorption of fat-soluble vitamins.
Explain how the red blood cells are broken down
Red blood cells are destroyed by Kupffer cells through the process called phagocytosis. Hemoglobin is converted into a yellow pigment called bilirubin. The protein is broken down to amino acids. Bilirubin is transported to bile and the released in the intestine. It is converted by a bacteria to a yellow pigment. This pigment is normal to feces.
State the definition of jaundice
Jaundice is the yellowish pigment that appears on the skin, which is caused by hyperbilirubinemia. It is the excess of the bilirubin in the blood and therefore body fluids are also yellow.
What are the major causes of jaundice?
- heavy drinking
- infections
- some medicines
What are the advantages of blood circulation?
- oxygenated blood reaches the body tissues
- high-pressure delivery of oxygenated blood to all regions
What is the branching sequence in the double circulation ?
aorta - artery - arterioles - capillaries - venules - veins - vena cava
What are the components of the blood and its functions ?
- water - solvent
- ions (sodium, chloride, potassium) - osmotic balance and membrane permeability.
- plasma proteins - clotting, defense
- substances transported by blood (nutrients, waste products)
- white blood cells (monocytes, neutrophils, lymphocytes) - defense, immunity
- platelets - blood clotting process
- red blood cells - transport of carbon dioxide and oxygen.
- phagocytes - ingesting bacteria
Define hemoglobin
It is the protein in red blood cells that consists of the globin and four heme groups.
Types of the vessels in the circulation system
- Arteries - carry blood away from the heart
- Veins- carry blood to the heart
- Capillaries - networks that link arteries and veins.
What are arteries?
The structures that convey blood at high pressure from the heart to the tissues of the body and lungs. It consists of the:
- narrow lumen - maintains high pressure
- thick wall - contains collagen
- arterial wall - contains muscles
Define capillaries
they exchange the materials between the cells in the tissues and blood travelling at low pressure.
What are 3 types of capillaries?
- continuous - they contain endothelial cells joined together by tight junctions to limit the permability of large molecules.
- fenestrated - they contain pores
- sinusoidal - they have open spaces and are permeable to large molecules
Define valves
Those are structures that are in veins and they ensure that blood flows in one direction, towards the heart.
Define heart
Muscular organ that has four chambers. Two upper chambers are called atria and they move the blood into the heart. Whereas, the two lower chambers are ventricles that pump blood out of the heart.
The heart consists of…
- Vena cava
- Right pulmonary artery
- Right atrium
- Tricuspid valve
- Right ventricle
- Left ventricle
- Bicuspid valve
- Semilunar valves
- Left atrium
- Left pulmonary artery
- Aorta
Explain the coronary circulation
Coronary arteries deliver oxygenated blood to the heart muscles. Cardiac veins remove the deoxygenated blood from the heart.
Myocardium
Circulation of the blood vessels of the heart muscle
Distinguish the cardiac cycle
When the heart contracts the blood is pumped out of the heart - systole. However, when the heart relaxes, the heart is filled with blood - diastole.
What is the difference between the AV valves and semilunar valves?
AV valves open when the blood enters the heart and then the pressure increases. Semilunar valves open when the blood leaves the heart so the pressure decreases.
Sympathetic nerve
It releases the adrenaline that increases the heart rate. This increases the blood pressure, metabolic activity, and breathing rate.
Parasympathetic nerve
It releases the acetylcholine which decreases the heart rate.
Define atherosclerosis
Sickness that damages the artery wall and the cholesterol builds up there. The wall loses its elasticity and leads to the blood clotting that blocks the artery. Therefore the coronary muscle dies as there is a lack of blood and oxygen incoming.
State the definition of the gaseous exchange
It is the process that takes place by diffusion and the molecules move along the concentration gradient.
Define diffusion
Passive movement of the molecules from the region of high concentration gradient a a region of low concentration gradient.
Factors affecting diffusion
- size of surface area
- concentration gradient
- length of the diffusion path
Explain the ventilation system
The pumping mechanism that moves the air into and out of the lungs, maintaining the concentration gradient for diffusion. Breathing increases the concentration gradient of oxygen between the alveoli in the lungs and blood.
What is thorax?
Area where lungs are located. The surfaces there are lined up by the plural membrane which secretes pleural fluid.
Function of pleural fluid
It protects the lungs from the friction during breathing movements.
The movement of air in the body
Air reaches the trachea and then passes through oesophagus. Then trachea divides into bronchi that divide into bronchioli and the air ends up in the air sacs (alveoli).
What happens with O2 and CO2 in the lungs cycle?
- o2 levels stay high in the lungs and diffuse into blood
- co2 levels stay low in the lungs and diffuse out of the blood
The lungs consist of…
- trachea
- superior right lobe
- middle lobe
- inferior right lobe
- bronchi
- lobar bronchus
- segmental bronchus
- superior left lobe
- middle left lobe
- inferior left lobe
What is the alveolar structure?
bronchiole, alveolar duct, alveoli, alveolar sac
What system wraps up around the alveoli clusters?
capillary system
State the function of pneumocytes
They carry the gas exchange
State the function of pneumocytes type II
Prevent the water from causing the sides of alveoli to adhere when air is exhaled from lungs. Also it provides the area from which CO2 can evaporate into air.
How alveoli minimize the diffusion distances
They have thin layers
What is the function of capillary networks in the alveoli?
They increase the capacity for gas exchange and contain fluids that help gases to be better diffused into the bloodstream.
Inspiration
When the pressure in the chest is less than atmospheric pressure, air will move into the lungs.
Expiration
When the pressure in the chest is higher than atmospheric pressure, air will move out of the lungs.
Emphysema
Lung condition where walls of alveoli lose their elasticity due to low surface area for the gas exchange. Cause: smoking.
How can gas exchange be efficient?
- High concentration gradients must be maintained in the alveoli
- Breathing increases the concentration of oxygen between the alveoli and the blood so it diffuses into blood
- Breathing out removes the CO2 and the concentration increases between the blood and alveoli.
What is the function of hemoglobin in the lungs?
hemoglobin binds to O2 in the lungs and unloads it somewhere else in the body.
What happens during asthma attack?
During astma attack the smooth muscle walls of the bronchi contract, blocking air flow into the lungs.
Why plasma proteins are pH buffers?
the pH of blood is required to stay within a very narrow tolerance range. Its range is maintained by plasma proteins. They contribute to increase in alkalinity.
What is the myoglobin?
It is used to store oxygen in the muscle tissues. it increases the efficiency of the respiration in the muscle tissues.
Why fetal hemoglobin is important?
It helps to take up oxygen at lower pressures.
State the definition of hormones
Chemical substances that are secreted from the cells of the endocrine glands. They circulate in the bloodstream (briefly).
Where hormones are broken down?
in the liver and the breakdown products are excreted in the kidneys.
Define endocrine system
Control system of ductless glands that secrete hormones.
Explain two types of hormone secretion
- Regulatory secretion - hormones are secreted in the secretory granules and released into bursts. It helps to secrete large amount of hormones over short period of time.
- Constitutive secretion - the cell does not secrete hormones, but secretes them from secretory vehicles.
Peptide hormones
short polypeptide chains that are hydrophilic and go through the regulatory secretion. we include the insulin and ADH.
Steroid hormones
lipids derived from cholesterol. they are lipophilic and go through the constitutive secretion. examples include oestrogens, testosterone
Amine hormones
they are derived from amino acids and they are hydrophilic. they undergo the regulatory secretion. examples include epinephrine
hydrophilic
cannot cross the membrane
lipophilic
can cross the membrane
How do steroid hormones activate the genes?
- They enter the target cells though the plasma membrane because they are lipophilic.
- The hormone-receptor complex is being created and it enters the nucleus.
- This complex binds to a specific DNA region.
- Steroid affects the gene expression Those hormones act as the transcriptional regulators.
How do polypeptide/amine hormones activate enzymes?
- Those hormones bind to the plasma membrane
- It activates the second messenger within the cell
- They act indirectly to change the cellular activity
Remember: the cannot enter the target cells!
Function of the amine hormones
- activation of enzymes
- secretion of specific molecules
- altering transcription
what are the main endocrine glands in the human body?
- hypothalamus (posterior pituitary gland and anterior pituitary gland)
- pineal gland
- thyroid glands
- parathyroid glands
- adrenal glands (adrenal cortex and adrenal medulla)
- islets of langerhans
- ovaries (female)
- testes (male)
Hormones produced by hypothalamus
Produces and secretes releasing hormones. It produces hormones such as ADH and oxytocin which are stored and released by the posterior pituitary gland.
What hormones posterior pituitary gland releases?
- oxytocin - uterine contractions and milk ejection
- ADH - released when we are dehydrated (stops peeing)
What hormones are released by the anterior pituitary gland
Releases hormones such as:
- thyroid stimulating hormone (thyroid gland): calcitonin and T3, T4 hormones.
- adrenocortico stimulating hormone (adrenal glands): cortex-cortisol and aldosterone, medulla- noradrelanine, norepinephrine.
- growth hormone: growth stimulation, protein synthesis.
- prolactin: increases milk production
- gonadotropins: ovaries- estrogens and progresterone, testes-androgens.
Pineal gland hormones
Secretes melatonin
Thyroid gland
secretes calcitonin and T3, T4 hormones (thyroxin hormones)
Parathyroid gland hormones
Secretes parathyroid hormones that oppose the calcitonin.
Adrenal cortex hormones
secretes cortisol and aldosterone
Adrenal medulla
secretes epinephrine and norepinephrine
Islets of Langerhans hormones
- alpha cells: secrete glucagon
- beta cells: secrete insulin
Ovaries hormones
secretes estrogens
Testes hormones
androgens
What is the antidiuretic hormone (ADH)?
It is the hormone that regulates the kidney processes. It helps to maintain the normal blood osmolarity.
State the roles of oxitocin
- in females oxitocin controls the milk secretion from mammary glands
- stimulates the ejection of milk
Posterior pituitary lobe
It releases hormones produced by neurosecretory cells of the hypothalamus. These hormones are released through the nerve cells to the posterior pituitary gland and then the hormones are released through the blood vessels to other endocrine glands.
Anterior pituitary lobe
Hypothalamus synthesises hormones that are released to the anterior pituitary gland through the portal vessel. The endocrine cells in this lobe stimulate the release of the hormones to other endocrine glands through the blood vessels.
How the hormonal regulation of growth works?
The growth hormone is secreted by the anterior pituitary gland and stimulates growth. The liver responds to the action of this hormone and releases insulin-like growth factors. It contributes to increase in the muscle mass.
What if GH is absent?
The skeleton of mature animal stop growing.
What if the hypersecretion of the GH occurs?
It leads to gigantism and the person is unusually tall but maintains the normal body proportions.
Explain the release of melatonin
When the photons of light stimulate the retinas of the eyes, nerve impulse is sent to a region of the hypothalamus called the suprachiasmatic nucleus (SNC). Then the signal is carried to pineal gland, where the production of melatonin is inhibited. The blood levels of melatonin fall, and as light levels decline the melatonin production increases which boosts blood levels.
The function of calcitonin
lowering the calcium levels
The function of thyroxine
They are essential for normal human growth and development. Thyroid hormones increase the metabolic rate and also help to control body temperature. They also help to regulate the synthesis of proteins.
What is the function of cortisol?
regulating the immune system
What is the function of aldosterone?
increasing the reabsorption of salt
Function of melatonin
regulates the biological rhythms
Function of epinephrine and norepinephrine
raising blood glucose levels and increasing the metabolic activities
Function of insulin
lowering the blood glucose levels
Function of the glucagon
raising blood glucose levels
Function of estrogens
development and maintenance of female secondary sex characteristics
What is the function of androgens?
support the sperm formation and promote development of male secondary sex characteristics
How does the ADH influence the water uptake in the kidney’s collecting ducts?
The binding of the ADH to receptor molecules leads to an increase in the number of aquaporin proteins inserted in the membranes of collecting duct cells. The channels recapture more water and that reduces the urine volume.
How temperature affects the thyroxine release?
- hotter temperature causes the hypothalamus to inhibit thyroxin release, which decreases the metabolic rate of the body to reduce heat production.
- colder temperatures cause the hypothalamus to stimulate the thyroxin release which increases the metabolic rate to generate more heat.
State the definition of hypothyroidism
Condition that occurs when there is thyroid hormone deficiency. Results in low metabolic activities and affects the physical development. Typical symptom can be the feeling like sleeping all the time.
State the definition of hyperthyroidism
Condition that occurs due to an excessive production of the thyroid hormone. The fluid accumulates behind the eyes - typical symptom.
What happens when there is an iodine deficiency?
the body cannot synthesize proper amounts of the thyroid hormone caused by low iodine in the diet.
How is leptin controlled?
It is the hormone that is produced by fat tissue found throughout the whole body. if someone reduces their caloric intake, their fat tissue will decrease and the leptin signal will also decrease. The hypothalamus responds to the reduced signal by increasing the desire to eat.
How is heat produced in our body?
The main source of heat is the metabolism. During the physical activity the skeletal muscles generate the great deal of heat as a waste product of respiration and contraction.
State the definition of endotherm
Organism that produces heat through the internal means such as muscle shivering or increasing its metabolism.
What is the hypoglycaemia?
The condition that occurs when the blood glucose levels fall and if it stays for too long, then coma could follow.
What is the hyperglycaemia?
The condition that occurs when the person has abnormally high concentration of blood glucose. It leads to a decrease in the water potential of the blood plasma.
Explain the mechanism for the regulation of glucose by endocrine glands
The endocrine glands that detect the excess or absence of the blood glucose levels are Islets of Langerhans. When the change in the blood sugar level in the pancreas decreases, alpha cells secrete glucagon. Blood glucose is raised by the synthesis of glucose from amino acids and fats. However, when the blood sugar levels increase, beta cells secrete insulin. The blood glucose levels decrease by an increased rate of respiration.
How the appetite control center is related to obesity?
Insuline resistance could reduce the activity of inhibitory neuron and reduce the amount of leptin releases. Leptin levels increase with body fat, though leptin resistance can develop. The action of blocking the neuron may lead to overeating and gaining weight.
What is the function of iodine during the women’s pregnancy?
Essential for the production of maternal and fetal thyroid hormones. It regulates the development of the fetal brain and nervous system.
Explain the menstrual cycle (exam worthy question)
- Menstruation: Endometrium sheds, triggered by low estrogen and progesterone.
- Follicular Phase: FSH stimulates follicle growth, producing estrogen, thickening endometrium.
- Ovulation: LH triggers egg release into fallopian tube.
- Luteal Phase: Corpus luteum forms, secreting progesterone and estrogen to support potential pregnancy.
- Menstruation (again): If no fertilization, corpus luteum degenerates, hormone levels drop, and endometrium sheds, starting a new cycle.
What is the movement within cells called?
cytoplasmic streaming
What is the movement within organisms called?
pumping action of the heart
What is the movement of whole organisms called?
locomotion
Types of skeleton systems
- external
- internal
Describe the exoskeletons
They surround and protect most of the body surface of insects. They contain the cuticle that consists of chitin (similar to cellulose). Muscles are attached to cuticles.
Describe the endoskeletons
Animals such as mammals have a internal skeleton buried with their soft tissues.
The function of bones and their types
Bones support and protect the body parts.
- the skull protects the brain, the eyes and ears
- vertebrae - protects the spinal cord
- rib cage - protects human lungs, human heart, and major blood vessels
What are the components of the locomotory system?
- bones
- joints
- tendons
- ligaments
- nerves
The function of joints
Junctions between the bones that permit the controlled movement.
Function of tendons
Those are connective tissues that attach muscles to bones.
Ligaments function
Ligaments are elastic connective tissues that connect the bones and help to prevent the dislocation of them. They form protective capsules around the joints.
Nerves function
They transmit nerve impulses from the central nervous system to muscles.
On what the strength of the resulting contraction depends on?
on how many muscle fibers the motor neuron controls
Why the skeletal muscles are antagonistic?
because when one contracts, the other one relaxes
What happens when the skeletal muscles are extended?
The lower arm is extended by contraction of the triceps muscle, accompanied by relaxation of the biceps muscle.
What happens when the skeletal muscles are flexed?
The lower arm is flexed by contraction of the biceps muscle, accompanied by relaxation of the triceps muscle.
Components of skeletal muscles
- ulna, humerus and radius
- biceps muscle
- triceps muscle
- capsule
- synovial membrane
- synovial fluid
- cartilage
Function of the humerus, radius and ulna
maintaining body posture and bringing its movements
What are the biceps muscles?
It is anchored to shoulder blade and contraction flexes the lower arm and stretches the triceps
What are the triceps muscles?
Anchored to shoulder blade so contraction extends the lower arms and stretches the biceps
Capsule function
Protection of the joints without restriction of movement
Synovial membrane and synovial fluid
Synovial membrane contains the synovial fluid which removes harmful leftovers from the worn bone.
Cartilage function
firm and flexible material that reduces friction
What is the hip joint
also a ball socket joint, located on upper arm which connects the shoulder blade with the humerus
Explain the movement at a hip joint
In the hip joint, the ball-like surface of one bone fits into a cup-like depression of another bone. This type of joint permits the movement in all of the free planes.
Explain the movement at the knee joint
The knee joint functions primary as the hinge joint. It restricts movement to one plane because of the shape of the articulating surfaces, and also the ligaments that hold the bones together.
Comparison of the hip joint and knee joint
Hip joint:
- type: ball socket
- articulating surfaces: between the acetabulum and head of femur
- permitted movement: circumduction
Knee joint:
- type: hinge
- articulating surfaces: between the femur and tibia and femur and patella
- permitted movement: flexion and extension
Describe the structure of skeletal muscles
- Bundle of thousand muscle fibers
- Tendon
- Connective tissue
What are muscle fibers?
group of modified muscle cells where many of them have joined to form a single mass of cytoplasm with many nuclei.
What are the protein fibers running through cytoplasm?
actin and myosin
What is the banding pattern of skeletal muscles?
Light bands are thin actin filments and the dark bands are myosin only and overlap actin and myosin. Whereas the sacromere consists of dark band and two light bands.
What are sacromeres?
basic units of muscles
What are muscles composed of?
tubular myofibrils
What are myofibrils composed of?
repeating sections of sacromeres that appear under microscope as dark and light bands
What is the structure of sacromere?
- thin filaments composed of protein actin
- thick filaments composed of myosin
- it is placed between two Z-lines
When skeletal muscle shortens?
during contraction because thick (myosin) and the thin(actin) filaments slide past one another.
How the shortening of muscles is possible (sliding-filament model)?
- because of the thick filaments (myosin) that have bulbous heads protruding from the filaments.
- the actin filaments have a complementary series of binding sites to which the bulbous head fit. In muscle fibers the binding sites carry tropomyosin.
What is the role of calcium and regulatory proteins in the muscles?
- actin plays crucial roles in muscle contraction and relaxation
- tropomyosin and troponin complex are bound to the actin strands of thin filaments.
- tropomyosin covers the myosin-binding sites along the thin filament that prevents the actin and myosin from interacting.
What happens when the Ca2+ accumulates in the cytosol?
It binds to troponin complex and expose the myosin-binding sites on the thin filament.
Explain the regulation of Ca2+ levels in the cytosol
- when it rises the thin and thick filments slide past each other and the muscle fiber contracts
- when it drops the binding sites are covered and contraction stops
What is the role of calcium ions in the muscle contraction?
- when a motor neuron sends a signal to the muscle contract, it causes the sacroplasmic reticulum to release calcium ions
- calcium ions react with troponin which triggers the removal of blocking molecule, trypomyosin.
- binding sites are exposed
How muscles contract (sliding-filament hypothesis)?
- Myosin head is bound to ATP and is in its low-energy configuration.
- The myosin head hydrolyzes ATP to ADP and phosphate and is in its high-energy configuration
- Myosin head binds to actin and forms a cross-bridge
- The ADP is released and the inorganic phosphate. The myosin returns to low-energy configuration, sliding the thin filament.
- Binding of a new molecule of ATP releases the myosin head from actin
- New cycle begins
What changes during the muscle contraction?
length of sacromere (not length of the filaments)
Functions of hepatocytes that change the chemical composition of plasma membrane
- regulates nutrient levels
- synthesizes cholesterol
- detoxifies blood
How liver regulates nutrient levels?
- glucose breakdown
- breakdown of excess amino acids
- storages vitamins such as A,D, B12 and iron
Explain the importance in the onset of juandice
- caused by high levels of bilirubin
- released into blood when excess is of yellow fluid is produced
- comes from breakdown of red blood cells
What are the health benefits of a diet high in fibre?
Prevents heart attack or cancer
What are essential amino acids?
They have to be included in the diet because the body cannot produce them
Consequences of Helicobacter infection in the stomach wall
causes inflammation of stomach lining and can increase the risk of developing gastric cancer
Production of the acid in the digestive system
- parietal cells release gastric juice
- gastric juice contains HCL created by proton pumps
- pH drops in the stomach
Why replicating experiments is important?
- no error
- gives precise and reliable data
Why tyrosine is an essential amino acid?
- produces chemical that support brain
- produce melanin which is the enzyme responsible for skin color
Nonessential amino acids
Nonessential amino acids can be made by the body.
In which part of the kidney the glomeruli will be found?
cortex
Why desert animals need to have long loops of Henle?
it allows them to conserve water
In the kidney ureter is connected directly to the…
medulla
The function of osmotic gradient in the medulla
it is created by loop of Henle and it permits the reabsoprtion of water from the collecting duct
What ultrafiltration means?
that only molecules below a certain size can pass through the filtration membrane
The hormone that controls water uptake in the collecting duct is
ADH released from posterior pituitary gland
What are the two types of the diseases that affect the immune system?
- infectious diseases
- non-infectious diseases
Infectious diseases
another organism or virus invades the host’s body and lives there parasitically
Non-infectious diseases
non-communicable diseases and cause conditions such as cardiovascular diseases and cancer
What are the two types of immunity?
- non-specific immunity allows the body to resist infections by a wide range of pathogens
- specific immunity- allows the body to resist infections of a specific pathogen
Immunity
ability to resist infection
3 types of barriers in the immune system
- external barrier (skin)
- internal barrier (mucus or cilia)
- phagocytotic barrier (gastric juice)
what is the structure of the external barrier-skin?
- it is covered with protein of dead cells of the epidermis - tough waterproof layer
- sebaceous glands are associated with hair follicles secrete sebum, which maintains skin moisture and lowers pH of the skin
- lower pH inhibits the growth bacteria
What is the defense against the tissue damage that causes the infectious diseases?
- phagocytes migrate to site of inflammation (chemotaxis)
- phagocytes and antibacterial compounds destroy the bacteria
What are some of the chemical barriers?
- lyzosome (saliva)
- acidic pH (stomach)
- antifungal peptides (intestinal tract)
How the blood clots?
- clothing prevents us from bleeding and protects us from pathogens
- when the blood vessel is damaged, collagen is exposed and it attracts platelets to exposed area
- they build a barrier that stops from losing too much blood
- to make the layer stronger it needs a protein fibrin
- the exposure of fibrin to outside chemical creates a sticky fibrin and it forms a mesh holding all the platelets together
- the clot develops a scab which protects the wound as it heals and the new skin layer is formed
What are platelets?
tiny cell fragment that float around in the blood
What is the innate immune system?
- second line of defense against the infectious diseases and it is non-specific response
What are the leukocytes that take part in the innate immune system?
- granulocytes - neutrophil, eosinophils, basophil
- monocytes - macrophage and dendritic cells
Function of neutrophils
- boost response of other immune cells
- destroy microorganisms
Function of eosinophils
- killing cells
- participate in the immediate allergic reactions
Function of basophils
- release enzymes to improve the blood flow
- prevent blood clots
Function of macrophages
- reactivation of oxygen and nitrogen species
- complementation of proteins
Function of dendritic cells
- responsible for production of cytokines that help to control the inflammation in the body
What is the phagocytosis (second line of defense)?
solid materials are ingested by a cell
Steps of phagocytosis
- attachement of the phagocyte to pathogen
- ingestion of pathogen
- fomartion of phagosome
- formation of phagolysosome
- destruction of pathogen and formation of residual body
- exocytosis of the vehicle removes the indigestible materials
What are two types of the phagocytes?
- neutrophils - become phagocytotic on the encountering material in the tissues
- macrophages - created from monocytes
What stimulates the specific immunity (third line of defense)?
proteins and other molecules on the surface of pathogens are recognized as foreign by the body and stimulate a specific response
What is the major histocompability complex?
It is the cell surface molecule encoded by a large gene family. Each individual MHC is genetically determined and is a feature that we inherit. It is present on the plasma membrane on the most of our cells.
What differentiates the MHC antigens from foreign antigens?
Lymphocytes
Function of lymphocytes
- recognize antigens and take steps to overcome them
- these cells divide rapidly and produce clones
Function of clone lymphocytes
- secrete antibody specific to certain antigen
Two categories of lymphocytes
- B-lymphocytes
- T-lymphocytes
B-lymphocytes
differentiate in the bone marrow and they secrete antibodies (humoral immunity)
T-lymphocytes
differentiate in the thymus and it attacks foreign cells ( cell mediated immunity)
How are the lymphocytes activated?
- during maturation lymphocytes develop the ability to recognize one specific antigen and self-tolerance
- when lymphocyte’s receptor binds to the antigen, they are activated
- they multiply and differentiate into cells
What are the antigen presenting cells?
pathogens engulf antigens and then present fragment of them on their surfaces where T cells can recognize them.
Stages of antibody production
- antigen binds to the antibody on the B-cell plasma membrane
- it is taken up by the exocytosis and then expressed at the MHC protein
- T cells bind to macrophage and they are activated and now called helper T-cells
- activated B cells divide rapidly and form a clone of plasma cells
- some B cells and T cells survive in the body as memory cells
How the memory cells are produced?
- small proportion of clones differentiate into long-lived memory cells that provide long-term immunity
Antibody cells
- protein called immunoglobulin
- made of polypeptide chains that are held together by disulphide bridges
Clonal selection
product of vast numbers of identical plasma cells
Polyclonal selection
- typical pathogen activates B-cells
- it triggers the secretion of antibodies that will attack the pathogen
- it will result in the more efficient destruction of pathogens
Modes of antibody action
- Making pathogens recognizable
- Neutralization of viruses and bacteria and toxins
- Antibodies cause sticking together of pathogens so they are prevented from entering into cells
What is the secondary immune response?
the immune system can eliminate the antigen, more rapidly and efficiently.
Antigens in red blood cells
- A: A antigen
- B: B antigen
- AB: A and B antigens
- O: none
What is the active humoral immunity?
when B cells encounter antigens and produce antibodies against them
What is the passive humoral immunity?
Passive immunity is provided when a person is given antibodies to a disease rather than producing them through his or her own immune system.
What are allergens ?
environmental substances that trigger an immune response.
Anaphylaxis
severe systemic allergic reactions that can be fatal if left untreated
How allergic reaction works?
- B cell encounters the allergen and it differentiates into plasma cell and makes the large quantities of antibody
- antibodies attach to mast cells an prime towards the allergen
- the exposure to allergen causes the antibodies to release large amounts of histamine which causes inflammation
What are the monoclonal antibodies?
- artificially produced antibodies to target one specific antigen
- they are used in cancer treatment
- cancers carry TAA (tumor-associated antigens)
- they block the tumor proteins and cancer cells are targeted and killed
What is the hybridoma?
- when the antibody producing B cells joins with the tumor cells, the cell become hybridized
- this cell is capable of synthesizing large quantities of antibodies
What are antibiotics?
- naturally occurring substances that slow down or kill microorganism
- they enter bacterial cells and disrupt the metabolic reactions of wall formation and growth
Why antibiotics are effective against the bacteria but no viruses?
- antibiotics work by interfering with specific metabolic processes, typically the synthesis and laying down of new wall materials
- viruses are not living cells and they do not have metabolism and cell walls
What is the HIV and AIDS?
HIV is identified as the cause of AIDS. it consists of two single strands of RNA which together with enzymes are enclosed by a protein coat. HIV is retrovirus.
How the HIV infection of white cells work?
- HIV binds to a host cell membrane and the core of the virus passes inside
- RNA and virus enzymes are released
- reverse transcriptase catalyzes the copying of the genetic code for the viruses’ RNA strands into DNA
- DNA enters the host nucleus and is spliced into host’s DNA of a chromosome
- the viral genes remain silent
How is AIDS developed ?
- activation of synthesis of viral mRNA
- it passes into cytoplasm and then it codes for viral proteins at ribosomes
- viral RNA enzymes are formed into viral cores
- they create new viruses
What are the effects of HIV?
- number of lymphocytes drops
- weight loss
- lack of ability to produce antibodies
What are the ways of infecting with HIV?
- sexual intercourse
- breastfeeding a newborn baby
- organ transplants
Negative selection of antigens
- recognizing self-antigen results in apoptosis
- failure to recognize the self-antigen results in the survival of the cell
Positive selection of the MHC
- recognizing self-MHC results in the survival
- failure to recognize the self MHC results in apoptosis
Benefits of vaccination
- complete eradication of diseases
- reduced death rate from a disease
- reduced long term disabilities
Dangers of vaccination
- excessive vaccination may reduce the effectiveness of the immune system to respond to new infections
- side effects
How HIV is diagnosed?
- Blood sample collection
- Antigen detection using specific antibodies
- Washing to remove unbound components
- Detection using enzyme-linked antibodies
- Color change indicates HIV presence
- Results interpretation: positive or negative.
Types of the nervous systems
- central (brain and spinal cord)
- peripheral (nerves)
How the nervous system works?
Specialized nerve cells that are organized into central and peripheral nerve systems link sense organs, muscles, and glands with the brain or spinal cord.
How the nerve system is built?
- nerve cells (neurons)
What are neurons?
Specialized for transmission of information in the form of impulses. Each neuron possesses a cell body (nucleus) and nerve fibers.
Nerve fibers
- dendrites
- axons
Dendrites
conduct impulses toward the cell body
Axons
conduct impulses away from the cell body (thinner than dendrites).
Structure of neuron
- cell body
- dendrites
- nucleus
- axon
- axoplasm (cytoplasm of axon)
- myelin sheath cells
- node of Ranvier
- motor end plate
- plasma membrane of neuron
Schwann cells
neuron is surrounded by them and they are wrapped around the axon of motor neurons and form myelin sheath
Myelin sheath
consists largely of lipid and has electrical resistance
Nodes of Ranvier
frequent junctions along the neuron and between the individual Schwann cells
3 main types of neurons
- sensory neurons
- interneurons
- motor neurons
Sensory neurons
They carry impulses from receptors to the spinal cord and the brain
Interneurons
Relay impulses from one neuron to another in the brain and spinal cord
Motor neurons
Carry impulses from the brain and spinal cord to effectors (usually muscles)
How are the signals carried from receptors?
They are carried as sense organs in the skin to the central nervous system in sensory neurons. Then from the CNS to effectors in motor neurons.
What is the effector?
organ of the body such as a muscle or a gland that responds to an impulse from motor neuron
What is the resting neuron?
- Neuron that is not conducting any electrical signal
- It is negatively charged and the cell becomes polarized
What is the resting potential?
The electrical potential difference across the plasma membrane when the cell is in a non-excited state.
Why resting potential exists?
- higher concentration of organic anions is found on the inside of the membrane, not the outside
- Na+ ions are largely prevented from moving across the membrane
What is meant by the nerve impulse?
When neuron is stimulated, the distribution of charges on each side of the membrane changes. Depolarization causes a burst of electrical activity to pass along the axon of the neuron.
- when an impulse spreads this way it is called an action potential.
Explain the depolarization
- stimulus causes the sodium facilitated diffusion channel to open
- sodium ions diffuse into the axoplasm
- axoplasm becomes more negative
- if there is an insufficient sodium ion, it fails to reach the threshold potential and it returns to resting potential
- if it reaches the resting potential it continues and changes from negative to positive potential
How the myelin sheath speeds up the conduction of nerve impulses?
It contains Nodes of Ranvier and by jumping from node to node, the impulse can travel more quickly than if it had to travel along the entire length of the nerve fibre
Where action potential is not generated?
In the regions between nodes
What is the salvatory conduction?
When the action potential jumps from node to node and greatly speeds up the rate of transmission.
What is the synapse?
Connection between two nerve cells
What synapse consists of?
- pre-synaptic neuron (axon terminal)
- neurotransmitter containing substances
- voltage gated sodium channel
- synaptic cleft (tiny gap between the nerve cells
- post-synaptic neuron (dendrite)
- ion channel receptor
What is the electrical synapse?
- channel proteins in the plasma membranes of both cells form gap junctions
- ions flow through them and allow the impulses to past directly to postsynaptic cell
What is the chemical synapse?
- The plasma membrane of the presynaptic and postsynaptic cells are separated by a narrow synaptic cell.
- Neurotransmitter molecules diffuse and bind to receptors. Binding opens channels to ion flow.
What if the stimulus is…
- below the threshold value - no action potential
- above the threshold value - action potential
What is the refractory period?
Period after excitation of neuron when the neuron fiber is not excitable. This happens due to excess sodium ions inside the fiber. However, after some time the resting potential is restored and action potential can be generated again.
Steps of synapse transmission
- impulse arrives at synapse, and triggers Ca2+ ion entry
- transmitter substance is released, diffuses to receptors of post-synaptic membrane
- transmitter substance binds, triggering entry of Na+ ions, and action potential in post-synaptic membrane
- enzymic inactivation of transmitter
- re-formation of transmitter substance vesicles
How does blocking of the synapse looks like?
- natural and synthetic chemicals can mimic neurotransmitters
- it stimulates the synapse even in the absence of the normal neurotransmitter
- chemical acts as inhibitor
- it will bind to the postsynaptic receptor but will not cause depolarization
- normal neurotransmitter cannot bind so no postsynaptic impulse occurs
Main functions of nervous system
- SENSORY INPUT: monitoring the changes occurring inside and outside the body
- INTEGRATION: interpreting sensory input and deciding what should be done at each moment
- MOTOR OUTPUT: activates muscles and glands
What goes inwards to the central nervous system and how (sensory division)?
- change or stimulus in the external or internal environment processed by visceral or somatic nerve fibers
- this is picked up by receptors
- then receptors will send the signals via nerves
- then it goes up to spinal cord and to the brain
What goes outwards to other nerve cells from the central nervous system (motor division)?
- signals from the brain are sent through motor nerve fibers to either somatic nervous system or autonomic nervous system
- AUTONOMIC NERVOUS SYSTEM: conduct impulses to cardiac muscles, smooth muscles, and glands by visceral motor (involuntary-unconscious). It divides into sympathetic and parasympathetic nerves
- SOMATIC NERVOUS SYSTEM: conducts impulses to skeletal muscles by somatic motor(voluntary-conscious)
Sympathetic division
Mobilizes body systems during activity
Parasympathetic division
Conserves energy and promotes house-keeping functions during rest
Sexual reproduction
The process that creates a new organism by combining the genetic material of 2 organisms
Fertilization in animals
The process involves the fusion of an ovum (oocyte) with a sperm which leads to an embryo development
Where oocytes are produced
ovaries
Where sperm is produced
testis
How female characteristics are developed?
- in the absence of Y chromosome no TDF is produced
- the lack of TDF allows the embryonic gonads to develop into ovaries
- in the absence of testosterone, the embryo develops female characteristics
TDF
Testis-determing factor
How male characteristics are developed?
- TDF is produced by a gene on the Y chromosome
- it induces medulla to develop into testes
- the testes produce testosterone, a hormone that initiates development of male characteristics
The male reproductive system
- bladder
- seminal vesicle
- prostate gland
- epididymis
- scrotum
- testis
- uretha
- penis
- sperm duct
What happens during ejaculation?
Sperm passes through the ejaculatory ducts and mixes with fluids from the seminal vesicles. The prostate forms the semen.
Seminal vehicles (male reproductive system)
Produce a yellowish viscous fluid rich in fructose
What is the prostatic fluid?
whitish, thin fluid containing proteolytic enzymes, citric acid, and lipids.
Function of bulbourethal glands (male reproductive system)
it takes place in sperm production and transports it into lumen of the uretha
Describe the structure of testes
- composed of seminiferous tubules which produce sperm
- each tubule is surrounded by the basement membrane which is lined by germline epithelium cells
- the germline epithelium will divide by mitosis to make spermatogonia
- developing smermatozoa are nourished by Sertoli cells
- interstitial cells produce male sex hormone, testosterone
Structure of sperm
- head (hydrolytic enzymes and DNA)
- mitochondria (energy)
- tail (swimming)
What leads to scurvy?
Lack of vitamin C and D
Difference between ghrelin and leptin
leptin lowers hunger levels, ghrelin increases hunger levels
Oogenesis
Formation of egg cell. Begins with meiosis in which diploid cell divides to form haploid cells. In females, this process starts before birth and continues throughout reproductive life. Each month, during menstrual cycle, one ovum undergoes maturation and is released from the ovary.
Structure of female reproductive system
- ovary
- oviduct
- opening to oviduct
- uterus
- cervix
- vagina
- vulva
Hormones in gestation/pregnancy
- progresterone - inhibits the secretion of oxytocin by the pituitary gland
- oxytocin- stimulates contraction of the muscular fibers
- gonadotropin - sex hormone that is initially secreted by the cells of blastocyst
Gestation
phase of fetus development in the womb
Formation of ovaries
- egg cells within primordial follicles undergo mitotic division
- egg cells with mature follicles begin mitotic division and then are released from the ovary as secondary oocytes
- epithelial layer separates ovarian tissue from the rest of the body
What ovaries contain?
- blood vessels
- corpus luteum
- secondary oocyte
- primary and tertiary follicle
- mature follicle
- germline epithelium
Structure of gamete
- haploid nucleus
- cytoplasm
- plasma membrane
- follicle cellls
- polar cell
- two centrioles
What if gamete is fertilized?
zygote begins to divide as it travels through the oviduct and implants into the lining of uterus
What if gamete is not fertilized?
egg travels through the oviduct to the uterus and leaves the body during menstruation
What are the stages of fertilization in human egg?
- sperm arrives and reacts with the egg
- the first sperm binds to the zona pellucida
- acrosome reaction is triggered and its contents are released
- sperm reaches the plasma membrane of the egg
- egg fuses and the fusion causes cortical reaction
- enzymes from the cortical granules prevent entry of more sperm
- mitosis occurs and two-cell embryo is produced
Embryo development
After fertilization, the embryo divides rapidly, forming a blastocyst from morula that implants into the uterus. The blastocyst then undergoes gastrulation, forming three germ layers that develop into organs and tissues. This process continues until a fully formed fetus is developed.
Function of placenta in fetus
provides nutrients and oxygen
Role of hormones in parturition (giving birth)
- end of pregnancy - fall in progesterone levels
- the posterior pituitary gland releases oxytocin
- uterine contraction secretes more oxytocin
How in vitro fertilization looks like?
- stopping normal menstruation cycle with drugs
- Hormone treatment to develop follicles
- extract multiple eggs with ovaries
- Fertilization occurs under controlled conditions = in vitro
- Pregnancy test is conducted to see if implantation was successful
what is spermatogenesis and how this process looks like?
Spermatogenesis is the process by which mature sperm cell is produced. It occurs in the seminiferous tubules of the testes.
- begins with spermatogonia
- those cells undergo mitosis to produce primary spermatocytes
- then they undergo DNA replication followed by meiosis I
- meiosis I results in the formation of two haploid secondary spermatocytes
- secondary spermatocyte undergo mitosis II leading to formation of four haploid spermatids
- they transform into mature sperm cells
Excretion
removal of the waste product from the body by metabolism.
What are nitrogenous compounds?
- come from breakdown of proteins, nucleic acids and amino acids.
- we include: urea, ammonia, uric acid.
Osmoregulation
the control of proper balance of water and dissolved substance.
How do kidney helps to maintain homeostasis in the body?
- they excrete urea (ammonia is converted into urea which is safely excreted).
- regulate amount of water
- maintain pH balance throughout the body.
How human urinary system looks like?
- blood is carried to the kidney by the renal artery and taken away by the renal vein
- it takes urine to the bladder
Structure of kidney
- renal cortex
- renal medulla
- both regions are supplied with blood by a renal artery and drained by renal vein
- nephrons
- pelvis
- ureter
- collecting duct
- fibrous capsule
- the urine is collected by renal pelvis and exits the kidney via ureter
What are nephrons?
basic units of structure and function of the kidney
Structure of nephron
- glomerus
- afferent arteriole
- efferent arteriole
- bowmans capsule
- proximal convoluted tubule
- descending and ascending limb of Henle
- loop of Henle
- distal convoluted tubule
- collecting duct
Through what layers does filtration takes place?
- endothelium of the blood capillary (thin)
- basement membrane of the blood capillaries (water and small solute molecules can pass through spaces between the fibers)
- epithelium of the renal capsule (made of podocytes)
How urine is formed?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
- Urine extrection
- Water reabsorption
Explain the glomerular filtration process
- blood flows from the renal arteries to the afferent arterioles into glomerulus
- the filtrate moves into Bowman’s space of the glomerulus
- the Bowman’s capsule filtrate this fluid
What happens in the tubular reabsorption?
- during tubular reabsorption fluid moves from the renal tubules into peritubular capillaries
- reabsorption starts in the proximal tubules
- those capillaries carry reabsorbed fluid into venous circulation
What happens in the tubular secretion?
- during tubular secretion fluid moves from the peritubular capillaries into the renal tubules and drains into collecting tubules
- renal tubules carry the fluid which eventually leaves the body in the form of urine
- substances that are secreted include K+, H+, NH4- and some drugs.
Function of podocytes
they allow the filtrate to pass rapidly and easily into the space of Bowman’s capsule as there are gaps between the cells.
Where large molecules can enter and cannot enter when it comes to renal capsule?
- can enter gaps between the capillary cells (fenestrations)
- cannot enter the basement membrane which is an ‘ultra- filter’
How proximal convoluted tubule cells are adapted for absorption?
- have large surface area due to microvilli
- numerous mitochondria
- closeness of blood capillaries (short distance in between)
- active transport channels in the membrane
What happens in the water reabsorption step?
- ADH travels in the blood to the kidneys where it increases the permeability of the distant convoluted tube and collecting ducts to water.
How does ADH influence water uptake in the kidney’s collecting ducts?
- binding ADH to receptor leads to temporary increase in the number of aquaporin proteins in the membranes of collecting duct cells
- additional aquaporin channels recapture more water, reducing urine volume.
How water reabsorption is controlled?
- as filtrate flows down the collecting duct the surrounding fluid is more concentrated.
- if the blood concentration rises osmoreceptors stimulate the neurosecretory cells to release ADH
- aquaporins are inserted to the duct wall by ADH so water is removed by the blood
- as blood concentration returns to normal, the ADH secretion stops
How loop of Henle works in habitats?
- the drier the habitat the greater the need to conserve water
What presence of glucose in urine indicates?
- diabetes which causes incomplete reabsorption
What presence of high quantities of proteins in urine may indicate?
- disease such as PKU or hormonal conditions such as pregnancy
What blood in urine indicates?
- cancer
- infection
What is kidney failure?
- kidney tubules fail to filter enough blood and fail to clear toxins from the blood
How kidney failure can be treated?
- transplant
- haemodialysis
How haemodialysis works?
- tube is placed in a large vein in arm and the blood circulates through the dialysis machine and is returned to the arm vein
- the dialysis fluid is a solution where the solutes are balanced to either cause or prevent diffusion
Why fish produce ammonia?
Ammonia is formed from the metabolism of protein and is the major waste product of fish. The majority of ammonia from fish is excreted through the gills, with relatively little being lost through urine and feces. Ammonia is also formed as uneaten feed or other organic matter in an aquarium decomposes.
