8. Animal Organogenesis And Circulation Flashcards
What is a gastrula?
An animal embryo with three layers of cells (endoderm, ectoderm, mesoderm) surrounding a central cavity with a small opening (blastopore) to the exterior.
What is invagination?
The process of being turned inside out or folded back on itself to form a cavity or pouch.
What is morphogenesis?
The origin and development of morphological characteristics.
What is embryogenesis?
The process of initiation and development of an embryo from a zygote.
What is a gastrocoel?
The primitive gut formed during gastrulation.
What do the germ layers develop into?
Every other type of tissue in the body.
The gastrulation of embryos only occurs in…?
Animals.
Why are diploblast body plans simpler than triploblast body plans?
Diploblasts lack certain structures and tissues derived from the mesoderm, such as muscles and most internal organs.
What is the classification of an animal where the blastospore forms the anus?
A deuterostome.
What is the classification of an animal where the blastospore forms the mouth?
A protostome.
What is a protostome?
An animal where the blastospore eventually forms the mouth.
What is a deuterostome?
An animal where the blastospore eventually forms the anus.
Unlike most other animals’ eggs, human eggs are…?
- Small.
- Contain very little nutrition for the developing embryo.
What are 4 steps of human embryonic development?
- The egg is released from the ovary into the oviduct, where it is fertilised.
- The zygote travels down the oviduct to the uterus over 6 days, undergoing cleavage to form a blastocyte (mammalian blastula).
- The outer layer of the blastocyte initiates the implementation of the embryo into the wall of the uterus on day 7.
- Extra embryonic layers start to form after about 10 days and gastrulation begins.
What are the 3 ways mammals give birth?
- Laying eggs. monotremes
- Birthing at an early developmental stage. marsupials
- Birthing fully developed offspring. humans and whales
What 2 things are considered adaptions for land animals to enable embryonic development in a fluid environment?
- Shells.
- The uterus.
What are the 4 extraembryonic membranes?
- Amnion.
- Chorion.
- Yolk sac. Vitellus
- Allantois.
What is the purpose of the amnion membrane?
Fiills with amniotic fluid, causing the ammion to expand and become the amniotic sac.
Provides a protective environment for the developing embryo.
What is the purpose of the chorion membrane?
The outermost membrane.
Largely used for gas exchange of O2 and CO2.
What is the purpose of the yolk sac membrane?
- Provides nutrition before the formation of the placenta.
- Produces RBCs.
- Gas exchange between mother and embryo in a mammal.
What is the purpose of the allantois membrane?
- Associated with the formation of the placenta and umbilical chord in mammals.
- Disposes of waste in reptiles.
What is the placenta?
An organ that develops in the uterus during pregnancy.
Provides oxygen and nutrients to a growing baby, as well as removing the baby’s waste products.
What is neurulation?
The process of the neural plate bending and fusing to form the hollow tube that will differentiate into the brain and spinal cord of the CNS.
A type of organogenesis.
What is the notochord?
A cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals.
What is the neural tube?
The structure that forms the early brain and spinal cord.
What are somites?
Precursor cells that give rise to important structures associated with the vertebrate body plan.
They eventually differentiate into skeletal muscle, cartilage, tendons, and vertebrae.
What are neural crest cells?
Embryonic cells pinched off during the formation of the neural tube that migrate extensively to form sensory and autonomic neurons.
They also produce parts of the teeth and skull bones.
What is induction?
The process of a group of cells or tissues influencing another group through close-range interactions.
What are 3 steps of neurulation?
- The neural plate forms the dorsal epidermis (ectoderm).
- The neural tube develops from the folding and pinching of the neural plate.
- The neural crest cells form between the epidermis and the neural tube.
Which precursor cells determine the migration paths of neural crest cells?
Somites.
Which structure helps embryonic cells migrate? How?
The cytoskeleton.
It enables cells to ‘crawl’ through the extracellular matrix by extending and retracting fibres.
What is the cytoskeleton?
A structure that helps cells maintain their shape and internal organisation while providing mechanical support for functions like division and movement.
Capable of rearranging - enabling the cell to change shape.
What mechanism is used to help with organ sculpting?
Cell apoptosis - programed cell death that kills off unnecessary cells.
How do phagocytes remove dead cells?
They recognise and engulf the dead cells before transferring them to lysosomes, where their cellular components are degraded for use.
What are pseudopodia?
Temporary projections of a cell.
Typically used for locomotion or phagocytosis.
What cells ingest foreign particles such as bacteria, carbon, dust, or dye?
Phagocytes.
What are lysosomes?
Membrane-bound organelles that contain digestive enzymes.
Used to break down excessive or worn-out cells, as well as invading viruses and bacteria.
What is interstitial fluid?
The fluid filling the spaces between cells in most animals.
What is circulatory fluid?
The fluid that moves around the internal structures of an organism.
What vessels slow down the movement of fluid and spread it over a large surface area to maximise gas exchange?
Capillaries.
What circuit moves blood from the heart to the lungs and back?
The pulmonary circuit.
What circuit moves blood from the heart to the rest of the body and back?
The systematic circuit.
How does the pulmonary circuit move blood?
- From the right side of the heart.
- To the lungs.
- Back to the left side of the heart.
How does the systematic circuit move blood?
- From the left side of the heart.
- To the rest of the body.
- Back to the right side of the heart.
Where does gas exchange occur?
From the cell’s cytoplasm to the surrounding interstitial fluid via the cell membrane.
What type of cells need gas exchange?
All of them!
What 2 gases cross the cell membrane in gas diffusion?
- Carbon Dioxide (CO2)
- Oxygen (O2)
Why can an amoeba diffuse directly into the external environment?
It has a high surface area to volume ratio.
What is diffusion?
A process resulting from the random motion of molecules from an area of high concentration to an area of low concentration.
The time taken for a substance to diffuse is proportional to…?
The distance needing to be travelled.
What is the difference in the concentrations of the molecules of two areas called?
The concentration gradient.
What is a gastrovascular cavity?
A simple digestive structure possessing only one opening for both foods and waste products.
Found in primitive invertebrates.
Why can primitive invertebrates (including hydras and jellyfish) directly diffuse?
- The outer and inner tissue layers of these organisms are bathed in water.
- The body wall is only two cells thick.
These creatures have no distinct circulatory system
What are the 3 basic components of a circulatory system?
- Circulatory fluid.
- Interconnecting vessels.
- A muscular pump (heart).
What animals require a circulatory system?
Those with a complicated body system.
What is hydrostatic pressure?
The pressure exerted by a fluid at equilibrium at any point in time due to the force of gravity.
What is the fluid in an open circulatory system called?
Haemolymph.
It acts as the interstitial fluid.
What is the fluid in a closed circulatory system called?
Blood.
It is separate from the interstitial fluid
What is the circulatory system in vertebrates often called?
The cardiovascular system.
It contains a heart as well as an extensive network of blood vessels and blood.
Arteries carry blood…?
Away from the heart.
Veins carry blood…?
Towards the heart.
What do arteries branch into?
Arterioles.
These, in turn, connect to the capillaries.
What are capillary beds?
Networks of capillaries that infiltrate tissues, diffusing gases, and chemicals into the interstitial fluid around the cells.
What do veins branch into?
Venules.
These occur where the capillaries converge to become venules, then veins
What are capillary walls like?
Thin and porous.
What is plasma?
The liquid martix in which blood cells are suspended.