Development 3 Flashcards
Tissues
a group of cells similar in structure that perform common or related function.
• Histology: study of tissues.
• Pathology: A branch of medical specialization concerned with the study of the morphologic aspects of disease.
Which of the following tissue types would you expect to find on a surface of the body that is subjected to friction?
A. Epithelial tissue
B. Connective tissue
C. Muscle tissue
D. Nervous tissue
A. Epithelial tissue
The four basic tissue types
- Epithelial (Covers)
- Connective (Supports)
- Muscle (Moves)
- Nervous (Controls)
Epithelial Tissue
2 major categories
- Covering and lining epithelium lines internal (hollow organs, body cavities, ducts) or external surfaces (skin).
- Glandular(lines internal organs and releases muscous and other fluids,)epithelium is formed by cells specialized in producing secretions.
The 5 characteristics
- Polarity
- Specialized contacts
- Supported by connective tissues
- Avascular, but innervated
- Regeneration
Polarity
Epithelial cells have polarity (top vs. bottom).
• Apical surface exposed to surface or cavity, borders open space
• Basal surface attached to underlying connective tissue, next to underlying connective tissue
Specialized Contacts
Epithelial cells need to be together to form a tight barrier.
To achieve this, adjacent epithelial cells form two types of connections:
• tight junctions (impermeable to substance)
• desmosomes (anchoring structure)
Specialized Contacts
Epithelial cells need to be together to form a tight barrier.
To achieve this, adjacent epithelial cells form two types of connections:
• tight junctions (impermeable to substance)
• desmosomes (anchoring structure)
Supported by Connective Tissues
All epithelia are supported by connective tissue.
Their boundary is known as the basement membrane.
• consists of basal lamina (secreted by epithelial layer) and reticular lamina (produced by connective, a layer that sometimes sits below the basal and serves to anchor the basal to connecting tissues
Cancerous cells
Not contained by the basement membrane can invade underlying tissues resulting in try spread of cancer(methasis)
Cancerous cells
Not contained by the basement membrane can invade underlying tissues resulting in try spread of cancer(methasis)
Avascular but inverted
Epithelial tissues does not contain blood vessels
How do epithelial cells receive nutrients
Through diffusion of substances from the underlying connective tissue, through the basement membrane or other transport mechanism from the apical and lateral surfaces of the cell
- epithelial tissues are supplied by nerve fibres(innervated)
Regenerative
Epithelial cells undergo rapid cell division to replace damaged cells (as long as they receive adequate nutrition).
Example:
The skin undergoes constant shedding by removing the superficial layer of the epithelium.
Classification of Epithelail Tissue
How many layers does the epithelium has
• Simple (single-layered)
• Stratified (multi-layered)
• Pseudostratified (one layer of cells that rest on the basement membrane, but appears to have several layers)
- appears stratified because the cell nuclei are at different levels
When would a simple epithelium be useful?
Absorption, secretion and filtration
When would a stratified epithelium be useful
High abrasion and protection
What is the cell shape
What is the cell shape?
• Squamous (flat)
• Cuboidal (as tall as they are wide)
• Columnar (taller than they are wide)
The shape of the nucleus conforms to that of the cell.
Transitional Epithelium
A special type of stratified epithelial tissue that change shape when stretched.
Other structures associated with the epithelial tissue
• Goblet cells: mucus-producing cells. Are a unicellular exocrine gland
• Cilia: cell structure that move materials across the cell surface.
Grandular Epithelium
contain glands that secrete aqueous fluid.
Depending on site of release, they are classified as:
• endocrine: internally secreting (example: hormones)
• exocrine: externally secreting (example: sweat)
- they are either unicellular or multicellular
Where would you find goblet cells?
In the epithelial linings of the intestinal and respiratory tracts
(Multicellular ecocrine gland)
Secretion is released
From a unit of cells which consists of a duct(the thing that collects it) and secretory unit(the thing that removes it)
Exocrine glands
Classified as:
Merocrine glands secrete products by exocytosis.
• Examples: salivary gland, pancreas
Apocrine glands pinches off at the apical side to release secretion.
• Examples: mammary gland and apocrine sweat gland
Holocrine glands completely ruptures to release secretion.
• Examples: sebaceous oil gland
Think of balloons
True or False: Connective tissue is the most abundant and widely distributed tissue type
True
The 4 classifications of connective tissue
- connective tissue proper
- cartilage
- bone
- blood(lymph)
Functions of connective tissues
The functions of connective tissue also vary significantly depending on the type:
• Bind, support and protect (bones, cartilage)
• Insulate (adipose tissue)
• Store reserve fuel (adipose tissue and bones)
• Transport substances within the body (blood and lymph)
They have 2 chartertistics
- Connective tissue consists of two major components: cells and extracellular matrix (ECM).
- Connective tissue types share the same cell lineage
ECM
Fill the space between cells
It’s made up of:
1. Protein fibres: collagen, elastic fibres and or reticular fibres
2. Ground substance: cell adhesion proteins, proteoglycans and interstitial fluid
ECM
Fill the space between cells
It’s made up of:
1. Protein fibres: collagen, elastic fibres and or reticular fibres
2. Ground substance: cell adhesion proteins, proteoglycans and interstitial fluid
If protein fibres would you expect to find in areas that undergo a lot of stretching and recoil
Elastic
Protein Fibres
All three types of fibres provide support in different ways.
Collagen fibre provides tensile strength (resist pulling and compression).
Elastic fibre allows for stretch and recoil.
Reticular fibre creates a mesh-like network to hold substances in place.
Connective tissue cells all come from
mesenchymal stem cells (MSCs).
MSCs first become -blast cells in different tissue types and actively secretes the ECM.
• Fibroblasts form connective tissue proper
• Chondroblasts form cartilage
• Osteoblasts form bones
• Hematopoietic stem cells form blood
The blast cells then mature into
-cyte cells that help maintain the health of the ЕСМ.
• Adipocytes (fat cells)
• Chondrocytes (cartilage cells)
• Osteocytes (bone cells)
• Leukocytes (white blood cells) and erythrocytes (red blood cells)
Connective tissue types are identified based on
• The cell types contained
• The type, amount and arrangement of protein fibres
• The nature of the ECM: liquid, gelatinous, or solid
Areolar Connective Tissue
Areola: small space.
Locations: widespread; found under the epithelial tissue
Major cell types: fibroblasts, some adipocytes and immune cell types (macrophages, mast cells and lymphocytes)
Functions:
• wraps and cushions organs
• supports and binds other tissues
Adipose Connective Tissue
Locations: under the skin, abdomen, breast, around kidneys, and eyeballs
Major cell types: adipocytes, *some immune cells
Functions:
• energy storage
• insulation and cushion
• supports and protects organs
Reticular Connective Tossues
Locations: lymph nodes, bone marrow and spleen
Major cell types: fibroblasts that produce reticular fibres and blood cells
Functions:
• forms an internal network called stroma to support blood cells
Regular Connective Tossue
Locations: lymph nodes, bone marrow and spleen
Major cell types: fibroblasts that produce reticular fibres and blood cells
Functions:
• forms an internal network called stroma to support blood cells
Regular Connective Tossue
Locations: lymph nodes, bone marrow and spleen
Major cell types: fibroblasts that produce reticular fibres and blood cells
Functions:
• forms an internal network called stroma to support blood cells
Irregular Connective Tissue
Locations: dermis of skin, coverings of organs and joint capsules
Major cell types: fibroblasts that produce collagen fibres organized in different directions
Functions:
• withstands tension in multiple directions
Elastic Connective Tissue
Locations: walls of large arteries and bronchial tubes
Major cell types: fibroblasts that produce large amounts of elastic fibres
Functions:
• allows for elastic recoil after stretching
Which one of the following has the most liquid ground substance?
A. Connective tissue proper
B. Cartilage
C. Bone tissue
D. Blood
D
Blood
Locations: within the blood vessels.
Major cell types: erythrocytes, leukocytes, lymphocytes, and megakaryote fragments (platelets).
The ECM of blood is the plasma.
