Lancelet Systems – Subphylum Cephalochordata
1.No Class for this
2.Be able to trace these from start to finish from memory

IV. Digestive System of Lancelet
1. Rostrum – most anterior end
2. Vestibule – hollow area behind the rostrum
3. Mouth – opens off the vestibule. (Note again, mouth after vestibule not before)
4. Wheel organ – acts to pump water into the vestibule
5. Pharynx
6. Gill Slits – perforations into the pharynx part of the digestive system
7. Gill Bars –act as filters from water moving through the gill slits
8. Atrium – a membrane structure that actually surrounds the pharynx
9. Atriopore  - a hole in the atrium that strains out water
10. Intestine
11. Cecum – a shunt off of the intestines (see this in most all Phylum Chordata – even mammals)
12. Anus
13. Keep in mind we have both water and food entering the mouth but the water leaves through the pharyngeal slits and food leaves the anus

V. Respiratory System of Lancelet
1. Water that enters also contains dissolved oxygen as well as food when enters the mouth
2. Gas exchange happens at gill slits
3. Thus gill slits serve two functions (systems): Digestive and respiration
4. deoxy water leaves via the atriopore

VI. Circulation System of Lancelet
1. Closed system of vessels
2. No distinct heart for pumping the blood
3. Ventral Aorta acts as the heart by peristaltic contractions
4. Arteries branch away from aorta and further help pumps deoxy blood
5. Arteries goes into a capillary bed (aka, cap bed)
6. Arteries leave cap bed not as veins but as “efferent arteries” and refuse together into a fused pair of dorsal aortas (aortae = plural of aorta) on each side of the pharynx.
7. DA carried oxy blood to posterior region.
8. Large veins return to ventral aorta

VII. Skeletal & Muscular of Lancelet
1. Notochord lies immediately dorsal to digestive system
2. Notochord is endoskeleton element
3. Notochord is flexible but hard rod that muscles use for contraction points
4. Myomeres – these are V-shaped muscles  in Lancelet
5. The notochord prevents the folding of the body when the myomeres contract

VIII. Nervous System of Lancelet
1. Dorsal nerve cord (NC)
2. Anterior end has cephalization (remember the lancelet is bilaterally sym.)
3. Anterior NC slightly expands out into a brain
4. Spinal nerves – branch out from the NC to innervate the myomeres
5. Note:
a. Innervate – when a nerve makes contact with any other structure than a neuron.
b. Enervate – to deprive of strength, to weaken, has nothing to do with neurons.

IX. Excretory System of Lancelet
1. Nephridia – ciliated tubules similar to ones with earthworms
2. Cilia beat to draw in the fluid.
3. Has closed end that makes contact with coelomic fluid and absorbs waste.
4. Have a collecting duct at opposite ends of tubules to the cilia and opens by means of a pore into the atrium.
5. Note: this isn’t like humans where filtration is through the blood, instead it’s through coelomic fluid

X. Reproductive System of Lancelet
1. Dioecious
2. Gonads in the atrium and anterior to the atriopore
3. Gametes come out through the atriopore.
4. Thus, atriopore used in 3 systems:
a. digestive
b. circulatory
c. reproduction