developmental biology & circulatory systems Flashcards
what are tissues and who possesses them
ensembles of similar cells that together carry out a specific function
- All animals except sponges
what formation was a milestone in the evolution of animals
epethelia - allows compartmentation and therefore specialised systems
how are germ layers created
during gastrulation
how many germ layers can animals have
DIPLOBLASTIC: 2 germ layers
or
TRIPLOBLASTIC: 3 germ layers
what are the 3 germ layers
- Ectoderm (outer layer): epidermis, nervous system
- Mesoderm: muscle, bones, blood vessels, blood cells and coelomocytes. Lining of coelom. Gonads
- Endoderm (inner layer): epithelial lining of multiple systems, especially the gastrointestinal and respiratory tracts
how many germ layers do cnidarians have and what are they
2 - diploblastic (no mesoderm)
- Ectoderm = epidermis (No brain or central nervous system) - can be separated from the gastric pouches
- Endoderm = gastrodermis (No separate muscles; musculo-epithelial cells)
in what animals did Extracellular digestion first appear
radial animals
what is the cavity called in cnidarians
coelenteron
name the 2 types of canals cnidarians have and what they do
- Interradial canals: take the food from the mouth to the margin
- Perradial canals: carry seawater inwards
*Nutrients from food circulates in seawater canals in the mesoglea
the circulatory system is a transport of…
Dissolved gases
Nutrients
Waste products
Hormones
advantages of Aquatic respiration
- Respiratory surface supported by water
- Respiratory surface will not dry out
- CO2 removal is easier
- Current atmospheric [CO2] is 400 ppm
- Seawater can hold much more CO2 (carbonate-buffering system)
disadvantages of Aquatic respiration
- Seawater contains ca. 35x less O2 than air [O2] ↓ as temp or salinity ↑
- Oxygen diffuses 10 000x slower in water than air
- Water is denser and more viscous - moves more slowly over the respiratory surface
what happens to [O2] when temp or salinity increases
decreases
explain gills as a respiratory surface
- Thin-walled extensions of the body
- Can be external or internal
- May be specialised (e.g. crustaceans, bivalves) or multipurpose (polychaete parapodia, echinoderm tubefeet)
what do Small animals rely on for efficient diffusion rates
every cell being close to the ambient medium - diffusion rate of O2 suggests they can be no more than 0.5 mm thick
what kind of animals use their whole body surface for respiration
Poriferans, cnidarians, acoelomate worms, small crustaceans
what kind of animals have no transport system / circulatory system
Porifera
Cnidaria, cnetophora
Platyhelminthes
Rotifera
Lophophores
Nematodes
*larger metazoans require transport systems
how many orders of magnitude are there
15
what is the smallest polychaete and crustacean
Dinophilus gyrociliatus
Stygotantulus stocki
what is the cavity (coelenteron) in diploblastic animals also used for
internal transport (circulation), hydrostatic support, excretion, reproduction
where does the body cavity form
within the mesoderm
what is the body cavity called if it is lined with mesoderm-derived epithelium
coelom
what is the body cavity called If it is not lined with an epithelium
pseudocoelom
Advantages of coeloms
- coelenteron can now become a specialised, unidirectional digestive tract
- Coelom and its lining mesothelium for hydrostatic support, circulation, reproduction and excretion
- Coeloms (together with blood-vascular systems) can act as transport systems for mass flow of internal fluids (allow animals to increase in size)
- Acoelomate organisms e.g. platyhelminths, must rely on diffusion - distance between any individual cell and the environment is physiologically limited
explain the coelom in echinoderms
large and complicated - Important for circulation and respiration
- Coelomic fluid is essentially seawater - but contains populations of cells (coelomocytes)
- Water vascular system is part of the coelomic system; seawater is drawn in through the madreporite, circulated and let out
how does the coelom relate to respiration in echinoderms
Small, fingerlike extensions of the coelom (papulae) protrude through the body wall and are responsible for respiration and waste removal
explain the coelom in animals with open blood systems e.g molluscs, brachiopods, arthropods
Coelom = greatly reduced - main body cavity = haemocoel, divided into blood-filled spaces that bathe all the tissues
explain circulation in molluscs
- slow
- Oxygenated (arterial) blood -> heart -> discharged through ventricle into haemocoel
- Venous (deoxygenated) blood enters the base of the gill, is oxygenated as it passes through the lamellae and then continues into ventricle
explain mollusc gills
- Pair of cnetidia (gills, sing. cnetidium) inside mantle cavity
- Each cnetidium = central axis + 2 lamellae
- Blood inside the gills flows in the opposite direction to the water flow
- Water current driven by cilia lining mantle cavity and on cnetidia
explain Cnetidia in bivalves
- highly specialised as feeding organs in lamellibranchs
- Greatly enlarged for filter feeding
what is Segmentation (metamerism)
- Bilateral pairs of fluid-filled coelomic cavities
- Compartments separated by mesenteries (longitudinal) and septa (transverse)
- Allows specialised functions (e.g. gonads, nephridial systems)
explain crustacean circulatory system
- variable
- Smaller crustaceans - poorly developed circulatory systems, often without any heart
- Large crustaceans can - well-developed circulatory systems and have modified thoracic or abdominal appendages into gills
explain decapod circulatory system
- no true veins, only arteries
- Oxygenated haemolymph (blood) flows from gills into the pericardial sinus
- It then flows into heart openings (ostia) during diastole
- The haemolymph is pumped out through the arteries during systole
- Haemolymph leaves the arteries and flows between the tissues (the haemocoel) to a series of ventral sinuses and then to the gills
- Crustacean heart is therefore bathed in oxygenated blood
what kind of animals have Closed circulatory systems
Annelids, phoronids, chordates, cephalopods
explain circulatory systems in annelids
- No true heart – contractions of dorsal longitudinal blood vessel drive blood forward
- Blood flows posteriorly through ventral blood vessel
explain Polychaete respiration
- Generally, body surface = insufficient for gaseous exchange
- Parapodial lobes as respiratory surfaces or specialised protusions
what are Respiratory pigments
Proteins that combine reversibly with oxygen and therefore increase the carrying capacity of the blood (most common = haemoglobin (Hb)
*O2 + CO2 can be transported in solution - but most animals use respiratory pigments (all end in “in”)
haemoglobin (Hb) characteristics
- Metalloprotein containing iron and haem groups
- Can be contained within corpuscles or in solution
- If contained within corpuscles, the concentration can be much higher without affecting the partial pressure in the blood
- Primarily for oxygen transport - but can also be used as an oxygen store or in a simpler form (myoglobin) - facilitates O2 diffusion
Haemocyanin (Hc) characteristics
- Copper-based metalloprotein distributed within the haemolymph of arthropods, molluscs and larval stages of certain insects
- Mollusc and arthropod haemocyanins are considered to have evolved from a common primordial protein
- Lower oxygen-carrying capacity than haemoglobin + cannot be contained within corpuscles
- Multiple functionalities (not just oxygen transport/storage) including immunity
how can CO2 be transported
- Reversibly bound to Hb
- As bicarbonate (HCO3)-
- In solution
