Interactive quizzes (pili na lang):
https://www.purposegames.com/game/villi-and-microvilli
https://www.purposegames.com/game/extracellular-matrix-game
Content:
Villi in the Small Intestine: Definition, Structure, and Function
The small intestine is a long, coiled tube in the digestive system responsible for the absorption
of nutrients. Though it's around 23 feet long, it fits inside the abdominal cavity due to its tightly
folded structure. While its flat surface area would only be about 5 square feet, the actual surface
area reaches about 3,200 square feet because of its highly specialized inner structures.
To increase its surface area for maximum absorption, the small intestine uses three key
features:
1. Circular folds – These are large ridges on the inner wall that form peaks and valleys,
increasing the surface area to about 16 square feet.
2. Villi (singular: villus) – These are finger-like projections about 1 millimeter long that stick out
from the circular folds. Each villus contains connective tissue, blood capillaries, and lacteals
(lymphatic vessels). Villi alone increases the surface area by around 162 square feet.
3. Microvilli – These are tiny hair-like extensions on the surface of absorptive cells found in each
villus. They are so numerous (around 129 billion) that they form a “brush border” visible under a
microscope. Microvilli contribute the most to the surface area.
Together, these structures allow the small intestine to absorb nutrients efficiently and quickly.
Function of Villi
The main role of the villi is nutrient absorption. The absorptive cells of the villi take in nutrients
like amino acids, sugars, and water-soluble vitamins, which are then passed into the blood
capillaries and circulated throughout the body. Fats and fat-soluble vitamins are absorbed into
lacteals, enter the lymphatic system, and then go into the bloodstream.
Additionally, the microvilli contain enzymes that help break down sugars, proteins, and nucleic
acids. These enzymes also enter the intestinal lumen when older villus cells shed, continuing to
aid in digestion. https://theory.labster.com/villi_microvilli/
ECM
Extracellular Matrix: Definition, Structure, and Function
DEFINITION
- The extracellular matrix (ECM) is the non-cellular component present within all tissues
and organs
https://pmc.ncbi.nlm.nih.gov/articles/PMC2995612/
STRUCTURE
- Made up of proteins and polysaccharides.
- In animal cells, the ECM is made up of an interwoven network of fibrous proteins
and glycosaminoglycans (GAGs). -> GAGs - long, linear polysaccharides (chains of
sugars) found in the extracellular matrix (ECM) and on cell surfaces
- It is a system made up of extracellular macromolecules and minerals that offers
both structural and biochemical support to nearby cells.
- Examples of macromolecules and minerals: collagen, enzymes, glycoproteins, and
hydroxyapatite
PROCESS of making ECM:
1. The components of the extracellular matrix are produced inside resident
cells and are secreted through exocytosis.
2. Once released, they integrate with the existing matrix.
FUNCTION
- Surrounds, supports, and gives structure to cells and tissues.
- ECM helps cells attach to and communicate with neighboring cells, which plays a vital
role in cell growth, cell movement, and other cell functions.
- Involved in tissue repair and protecting cells from viral diseases.
- Initiates crucial biochemical and biomechanical cues that are required for tissue
morphogenesis, differentiation and homeostasis. (https://pmc.ncbi.nlm.nih.gov/articles/PMC2995612/)
- Anomalies in the ECM can lead to risks of developing certain diseases, such as cancer.
https://www.cancer.gov/publications/dictionaries/cancer-terms/def/extracellular-matrix
ADDITIONAL INFO:
(Relation to Animal and Plant cells)
Both plant cells and animal cells have ECM.
https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_(Bou
ndless)/04%3A_Cell_Structure/4.18%3A_Connections_between_Cells_and_Cellular_Activities_-_
Extracellular_Matrix_of_Animal_Cells
● In animal cells, the extracellular matrix consists of a combination of proteins and
carbohydrates.
● It is found surrounding outside the cell membrane.
● Its primary roles include facilitating communication between cells and helping in the
formation of tissues.
● Communication between tissues begins when a molecule in the matrix attaches to a
receptor, triggering structural changes that generate chemical signals, which then alter
the cell’s internal activities.
PLANTS
- What is the Extracellular Matrix in Plant cells? Cell wall.
● The plant cell wall is a complex form of extracellular matrix that surrounds every plant
cell. In 1663, Robert Hooke was able to observe the thick cork cell walls using an early
microscope, which allowed him to identify and name “cells” for the first time.
● The walls of adjacent plant cells are fused together, creating the complete structure of
the plant. These walls are typically thicker, more durable, and, most notably, much more
rigid than the extracellular matrix found in animal cells.
● As early plant cells developed stiff walls—sometimes several micrometers thick—they
lost the ability to move and instead adopted a stationary lifestyle, a trait that continues in
all modern plants.
https://www.ncbi.nlm.nih.gov/books/NBK26928
PARTS of ECM
QUIZ: https://www.purposegames.com/game/extracellular-matrix-game
Both polysaccharide and proteoglycan molecules acts as the building blocks that forms the
ECM
Polysaccharide Molecule - (In plants, cellulose is the primary structural polysaccharide in the cell wall, providing
strength and support. Animals also have polysaccharides in their ECM, such as hyaluronic acid and
glycosaminoglycans (GAGs), which contribute to tissue structure, hydration, and cell signaling.)
Proteoglycan Molecule - (a class of molecules found in the extracellular matrix of animal tissues. They consist of a
protein core to which one or more glycosaminoglycan (GAG) chains are covalently attached.)
Proteoglycan Complex - Looks similar to a tree that contains the center branch with is the core
protein and with branches which is associated to glycosaminoglycans
(a big, sponge-like structure. It is composed of a core protein to which several polysaccharide chains, also known as
glycosaminoglycans or GAGs, are linked.)
Microfilaments of Cytoskeleton - Act as railroad tracks that guides the pathway and provides
support for movement
(also known as actin filaments, are the thinnest components of the cytoskeleton, primarily composed of the protein
actin.)
Collagen Fiber - Similar to the metal rods used in construction, collagen fiber provides strength
which withstands potential damaging occasions
(strong, flexible protein fibers that form the main component of connective tissues in the body. )
Integrin - They act as a radio that connects two places and is responsible for signaling and
communication
(transmembrane receptor proteins that link the cell's cytoskeleton and extracellular matrix (ECM). They are essential
for signaling, communication, and cell adhesion.)
