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BIOL 111 Study Guide - Final Guide: Gastrodermis, Mesoglea, Cardiac Muscle

Biology (Sci)
Course Code
BIOL 111
Suzanne Gray
Study Guide

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Phylum Annelida Class Hydrozoan Hydra
No medusa stage, small polyp
Capture prey by using toxic stings from within their cnidocytes
Food enters into the mouth and then into the gastrovascular cavity where
intracellular digestion occurs by the gastrodermal cells
Indigestible food is then voided out of the mouth
Uses basal disc (foot) to remain attached to the substrate
Extends tentacles and body columns
Moves by gliding, somersaulting and floating on bubbles of gas
Sexual Reproduction: involves the union of a sperm and egg (gametes)
to produce a zygote
Sperm and egg are located in the gonads (small mounds found in
the epidermis)
Sperm is produced in the testes (upper surface, close to the
One egg is produced in each ovary (lower surface, close to the
Ovaries are generally bigger than the testes
Hermaphrodites: organism has the capability to produce both
types of gonads and gametes
Using occurs in the fall, sperm is released into the water and
enters the ovary through a hole
in the epidermis, in order to reach the egg.
Zygote then produces a hard covering and drops off the sediment
remaining dormant until spring.
Hypostome: conical elevation, with the mouth as its tip (mouth acts as
entrance and exit)
Tentacles: food capturing arms that radiate from the hypostome (contain
Gastrovascular cavity: where food absorption and digestion occurs, gas
exchange also occurs in the gastrodermis and epidermis
Basal disc: foot, attaches to the substrate and assists in locomotion
Body Column: contains the mesoglea (a thin, gelatinous layer between
the epidermis and gastrodermis
Epidermis: outer epithelial layer of cells
Gastrodermis: inner epithelial layer of cells
Cell Types
Epitheliomuscular cells: act as epithelial cells by covering and lining the
surfaces, act as muscular cells by containing muscular contractive fibers
(assist in movement)
Longitudinal muscle fibers: found in the epidermis
Circular muscle fibers: found in the gastrodermis
Cnidocytes: located in the epidermis, contain nematocytes (which are
induced by cnidocils to produce a toxic sting)
Cnidocils: bristle-like projections on the outer surface o the cnidocytes
Neurons: nerve cells that run along the epidermis and gastrodermis,
form nerve nets in each tissue layer, while the mesoglea attach’s the
nerve nets to one another
Sensory cells: nerve cells that are sensitive to touch or chemicals in the
water, relay the message back to the nerve nets to then undergo
coordinated muscular movement
Gland cells: located in the epidermis of the foot, secrete a sticky
substance which allows the foot to remain bound to the substrate, also
found in the gastrodermis to produce digestive enzymes
Interstitial cells: totipotent cells act as stem cells, able to divide and
differentiation, located between the epitheliomuscular/epidermis
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