The Tissue Level Flashcards
What is a tissue?
a group of cells with a common embryological origin that function together to do specialized activities
What is histology?
the science that study the tissues
What are the tissues of the body?
epithelial, connective, muscular, nervous
How do the cells within tissues remain anchored to other cells or structures?
by points of contact called cell junctions
What are the types of cell junctions?
tight, adherens, desmosomes, hemidesmosomes, gap
What are tight junctions?
web-like strands of transmembrane proteins that fuse adjacent membranes, it prevents the passage of substances between the cells
What is an adherens junction?
transmembrane proteins and microfilaments form a dense layer of protein on the inside of the membrane called the plaque, resists separation of cells during contractile activites
What connects the plaques in an adherens junction, what does it form?
glycoproteins called cadherins on both cells connect the plaques and from the adhesion belt
What are desmosomes?
similar to adherens junctions but the plaque does not attach to microfilaments, the plaque attaches to the intermediate filaments, weld-like
What is the strongest cell junction?
desmosomes, weld like junctions are the strongest and prevent cells separation under tension during contraction
What are hemidesmosomes?
half a desmosome, glycoproteins are integrins not cadherins, they anchor cells to the basement membrane, not to each other
What are gap junctions?
the plasma membranes are not fused (there is a gap in between), connexin proteins form fluid-filled channels in between the cells called connexeons
What are connexons?
connexin proteins forming a fluid filled channel between cells in gap junctions
What do gap junctions allow?
for physical intercellular communications
What is epithelial tissue?
the covering and lining tissues for surfaces, cavities, and ducts, also forms glands
What are the general features of epithelial tissue?
densely packed and arranged in sheets, many cell junctions, mitosis occurs frequently, attach to and supported by a basement membrane, is avascular but it does have a nerve supply, selective barrier, provide protective and secretory surfaces for the body, combine with nervous tissue to form special organs
What special organs can be formed when epithelial tissues combine with nervous tissue?
smell, hearing, vision, touch
What is an apical surface?
epithelial tissues always have this free surface that may contain cilia
What is a basal surface?
on epithelial tissue that is adhered to a basement membrane
What is a basement membrane?
a thin extracellular layer composed of basal lamina and reticular lamina.
What is the basal lamina of the basement membrane?
part of the hemidesmosome, made of proteins secreted by epithelial cells: laminin, collagen
What is the reticular lamina of the basement membrane?
made of collagen secreted by the fibroblasts of the connective tissue underneath
What are the functions of the basement membrane?
attaches and supports the overlying cells, provides surface for cell migration in growing and healing, restrict the passage of large molecules (filtration of blood in kidneys)
True or false: epithelial tissue has its own blood supply that supports the connective tissue underneath
False: has no blood supply, requires support from the connective tissue underneath
How are substances exchanged between the epithelial tissue and the connective tissue underneath?
exchanged by diffusion through the basement membrane
What are the two types of epithelial tissue?
covering epithelium, glandular epithelium
True or false: glands are always formed by 3 or more cells
false: a gland can be a single cell or a mass of epithelial cells adapted for secretion
What is a goblet cell?
a gland that is a single cell
Where do glandular cells lie?
in clusters deep to the covering and lining epithelium
What are the two types of glands?
exocrine and endocrine
What do exocrine glands do?
Secretes into ducts, onto surfaces
What do endocrine glands do?
Secretes hormones into the blood in the absence of ducts
True or false: some glands contain both exocrine and endocrine tissues
True, the Pancreas
give an example of an exocrine gland
Sweat gland
What type of exocrine glands are the most common?
Multicellular exocrine glands. Simple Tubular, Acinar or Branched Acinar
What do unicellular exocrine glands do?
Goblet cells secrete mucus onto the apical surface
What is the structural classification of exocrine glands
1. Simple gland: Duct does not branch • Tubular glands • Coiled or branched Tubular glands • Branched Acinar (alveolar)
2. Compound gland: Duct branches • Tubular glands • Acinar (alveolar) • Tubulo-acinar gland
What is the function classification of exocrine glands?
- Merocrine glands (most common type)
• Release substances by exocytosis - Apocrine glands
• The apical portion of the cell is released by exocytosis - Holocrine glands
• The entire cell ruptures and becomes the secretion
What is the most common type of functional classification of exocrine glands?
- Merocrine glands (most common type)
• Release substances by exocytosis
What do merocrine glands do?
• Release substances by exocytosis
What do apocrine glands do?
The apical portion of the cell is released by exocytosis
What do holocrine glands do?
The entire cell ruptures and becomes the secretion
What do endocrine glands do?
Secrete the hormones into the blood stream in the absence of a duct
What are the major endocrine glands in the body?
Pineal, Hypothalamus, Pituitary, Thyroid, Parathyroids, Thymus, Adrenals, Pancreas, Ovary/Testes
What is the most abundant and widely distributed tissue in the body?
The Connective Tissues
Connects, binds, supports, stores energy, and provides immunity
What are the functions of connective tissue?
Connects, binds, supports, stores energy, and provides immunity
True or false: connective tissue always occurs in body surfaces
Do not occur in body surfaces
Connective tissue is highly vascular except in ___________ and ________
cartilage and tendons
Connective tissue is well nerve supplied except in ______________
cartilage
What does connective tissue consist of?
Two types of cells:
- Immature
- Mature
What are the two types of cells in connective tissue?
- Immature
2. Mature
Describe immature cells in connective tissue. Give three examples
Capable of reproducing and secreting the matrix: suffix–blast
• Fibroblasts
• Chondroblasts
• Osteoblasts
Describe mature cells. Give three examples
Reduced capacity for reproduction and matrix secretion: suffix -cyte
• Fibrocytes
• Chondrocytes
• Osteocytes
What are the six cells of connective tissues?
- Fibroblasts:
• Present in all general connective tissues
• The most numerous
• Secrete the fibers and ground substance of the matrix
2. Macrophages: • Develop from monocytes (a WBC) • Two types: 1. Fixed macrophages 2. Wandering macrophages
- Plasma cells:
• Developed from the B lymphocytes
• Secrete the antibodies - Mast cells:
• Abundant alongside blood vessels of connective tissue
• Produce and release histamine
• Can ingest and kill bacteria - Adipocytes:
• Fat cells, store the triglycerides - Leukocytes:
• Neutrophils: present in infections
• Eosinophils: present in allergic responses and parasitic infections
What are the characteristics of fibroblasts?
Present in all general connective tissues
• The most numerous
• Secrete the fibers and ground substance of the matrix
What are the characteristics of macrophages
Develop from monocytes (a WBC)
• Two types:
1. Fixed macrophages
2. Wandering macrophages
What are the characteristics of plasma cells?
Developed from the B lymphocytes
• Secrete the antibodies
What are the characteristics of mast cells?
Abundant alongside blood vessels of connective tissue
• Produce and release histamine
• Can ingest and kill bacteria
What are the characteristics of adipocytes?
Fat cells, store the triglycerides
What are the characteristics of leukocytes?
Neutrophils: present in infections
• Eosinophils: present in allergic responses and parasitic infections
What does the extracellular matrix of connective tissue consist of?
- Ground substance
2. Fibers
The ground substance of the matrix may be _____, _____, ______, or _____
fluid, semifluid, gel, or calcified
What are the functions of the ground substance of the matrix?
- Supports and binds cells
- Stores water
- Medium for substance exchange
What does the ground substance of the matrix contain?
Contains water and many organic molecules
What are the organic molecules in the ground substance of the matrix?
Glycoaminoglycans (GAGs):
• They trap water and make the ground substance jellylike
Hyaluronic acid:
• Lubricates joints, helps maintain the shape of eyeball
• WBCs, sperm, and some bacteria produce hyaluronidase helping them move
easier in connective tissues
Chondroitin sulfate:
• Provides support and adhesiveness in cartilage, bone, skin, and blood vessels
What do glycoaminoglycans (GAGs) do in the ground substance of the matrix?
They trap water and make the ground substance jellylike
What does hyaluronic acid do in the ground substance of the matrix?
Lubricates joints, helps maintain the shape of eyeball
• WBCs, sperm, and some bacteria produce hyaluronidase helping them move
easier in connective tissues
What do chondroitin sulfate do in the ground substance of the matrix?
Provides support and adhesiveness in cartilage, bone, skin, and blood vessels
What are the functions of fibers in connective tissue?
Fibers function strengthening and supporting connective tissues
What are the three kinds of fibres in connective tissues?
- Collagen fibers
- Elastic fibers
- Reticular fibers
What is the most abundant protein in the body?
Collagen is the most abundant
protein in the body (25% of total)
What are the characteristics of collagen fibres?
In cartilage and bones:
• Form association with surrounding molecules
• In cartilage, collagen is surrounded by water, giving it cushioning effect
In dense connective tissues:
• Occur in parallel bundles
• Add tensile strength to the tissue
What do collagen fibres do in cartilage and bones?
Form association with surrounding molecules
• In cartilage, collagen is surrounded by water, giving it cushioning effect
What do collagen fibers do in dense connective tissues?
Occur in parallel bundles
• Add tensile strength to the tissue
Describe elastic fibers
Smaller in diameter than collagen
Made of protein elastin surrounded by fibrillin for added strength and stability
Form fibrous network within connective tissue
Can be stretched up to 150% without breaking
Plentiful in skin, blood vessels, and lungs
What are the characteristics of reticular fibers?
Consist of fine bundles of collagen with glycoprotein coating. Produced by the
fibroblasts. Thinner than collagen
Reticular fibers form the stroma of soft organs such as:
- Spleen
* Lymph nodes
