Topic 6 - Tissues And Organs Flashcards
How are animals and plants multicellular
They are made up of large numbers of cells
What are tissues
They are groups of cells of the same type performing a particular function
What are organs
They are structures made of several tissues that work together to carry out a number of functions
What is the leaf
An organ of photosynthesis with not just photsynthetic tissue, but other tissues that provide for gaseous exchange, transport and protection
What is the ileum
The organ, in the small intestine, that is concerned with the final stages of digestion, the absorption of the products of digestion, and the movement of undigested material along to the large intestine
How is a vast surface area for digestion and absorption provided in the ileum
Folds in the inner surface of the intestinal wall
Projections called villi that are present on the folded surface of the wall
Microscopic projections called microvilli on the cell-surface membranes of columnar epithelial cells that line the villi
What are the 5 distinct layers of the ileum
Mucosa Muscularis Mucosa Submucosa Muscularis externa Serosa
What is the function of the columnar epithelium
They provide a huge surface area for digestion and for the absorption of the products of digestion. Some substances are taken up partly by diffusion and partly by active transport
What is the function of Goblet Cells
These cells secrete mucus. Mucus is slimy, it protects the epithelium from the action of digestive enzymes and lubricates the lining as solid material is pushed along
What is the function of the villi
These finger-like projections increase the surface-area for the absorption of the products of digestion. The villi contain blood capillaries into which amino acids and monosaccharides are absorbed, and lacteals into which fats are absorbed
What are lacteals
Blind-ending lymph vessels
What is the function of the Crypts of Lieberkühn
The cells lining the bottom of the crypts are in a state of continuous division; new cells are continuously being pushed up by the division of cells deeper down.
What is the function of the Muscularis Mucosa
The muscle fibres contract to cause movement of the villi, so improving contact with the products of digestion
What is the function of the Submucosa
The Submucosa contains blood vessels, including venules of the hepatic portal vein and lymphatic vessels, supported by connective tissue
What does Muscularis Externa consist of
Circular muscle and longitudinal muscle
What do contractions of the longitudinal muscle cause
Pendulum movement
What do contractions of the circular muscle cause
Local constrictions
What do coordinated contractions of the circular muscle do
Push food along the gut by Peristalsis
What is the function of the Serosa
The outer layer of connective tissue serves to protect and support the gut
What is the function of the Upper Epidermis
The cells of the upper epidermis lack chloroplasts since their role is protective. They secrete a waxy cuticle that provides waterproofing and reduces water loss
What is the function of the Palisade Mesophyll
The Palisade layer, in the upper half of the leaf, has layers of tightly packed cells, each with abundant chloroplasts. It is adapted for maximal light absorption. This is the main photosynthetic region of the leaf
What is the function of the Spongy Mesophyll
The Mesophyll in the lower half of the leaf contains large air spaces. Gaseous exchange between these air spaces and the atmosphere can take place via numerous pores. Spongy mesophyll cells also contain chloroplasts and are photosynthetic
What is the function of xylem vessels
Xylem vessels supply the leaf with water and inorganic ions
What is the function of Phloem sieve tubes
Phloem sieve tubes transport sucrose away from the leaf
What is the function of the Lower Epidermis
The cells lack chloroplasts. The cuticle secreted on the lower surface is thinner than that on the upper surface since it is not exposed directly to the Sun
What is the function of Stomata
The lower epidermis contains numerous stomata, which allows gaseous exchange. They also allows water vapour to diffuse easily out of the leaf. Each stoma is surrounded by a pair of guard cells, which cause it to close at night and so water loss by transpiration is minimised
