Tissues Flashcards
Types of tissue
1) Epithelial
2) Connective
3) Muscle
4) Nervous
Epithelial tissue
- Sheets of cells that cover and line other tissues
- They protect underlying tissues and may act to filter biochemical substances
- Each epithelial cell has an apical surface and basal surface
- Apical surface - faces outside of the organ
- Basal surface - faces the basal lamina (base layer) and blood vessels
- Lateral surfaces are connected to neighbouring cells by junctional complexes
Types of Cellular junctions
1) Tight junctions - fusion of layers, no leaks. Urinary bladder, digestive tract
2) Desmosomes - mechanical interlocking, repeated tension and scratching; skin and heart
3) Gap junctions - tubular proteins connect to allow exchange; intestinal epithelial cells, heart and smooth muscle tissue
Classification of epithelial tissue
- Number of layers of cells: Simple ( one layer) or stratified (multiple layers)
- Shape of the cells: Squamous, cuboidal and columnar
- Presence of surface specialisations: Cilia, Keratin etc
Surface specialisations
- Smooth
- Villi - in small intestines, made up of cells lined with microvilli
- Cilia - Help transport materials
- Keratin - Protein made by cells
Simple squamous epithelium
- Fragile and thin
- Found lining surfaces involved in the passage of either gas or liquid
- Flat and smooth
Simple cuboidal epithelium
- Single layer of cube-shaped cells
- Round, dark staining nuclei aligned in a single row
- Occurs in areas of the body where secretion and absorption takes place (linen the renal tubules - kidney)
Simple columnar epithelium
- Elongated and closely packed together
- Nuclei aligned in a row at the base of the cell near the basement membrane
- Found in many excretory ducts was well as in the digestive tract
- Digestive tract tissue is covered by an apical (surface) specialisation
Stratified squamous epithelium
- Multilayered
- Occurs in areas of the body subject to mechanical and chemical stresses
- Protect underlying tissues
- Found in skin, oral cavity and oesophagus
Stratified cuboidal epithelium
- Usually 2 layers of cuboidal cells
- Found primarily along large excretory ducts
- Protects underlying tissues
Stratified columnar epithelium
- Found only in select parts of the respiratory, digestive, reproductive systems and along some excretory ducts
- Function in secretion and protection
Pseudostratified columnar epithelium
- Cell nuclei are found oat different levels across the length id the tissue
- Found in the respiratory tract and in portions of the male reproductive tract
Transitional epithelium
- Stratified epithelium with a basal layer of cuboidal or columnar cells and a superficial layer of cuboidal or squamous cells
- Found in areas of the body required to expand and contract as part of their normal function
- Found mainly in the bladder and urethra
Exocrine and endocrine glands
1) Exocrine
- Discharge secretions via ducts directly into local areas (except goblet cells)
- Unicellular or multicellular
2) Endocrine
- Glands that do not have ducts or tubules and whose secretions are distributed throughout the body
- Produce and secrete hormones into the bloodstream or the lymphatic system
- Multicellular
Exocrine cell types
- Apocrine glands - store their secretions and then release them in enclosed membranes
- Merocrine glands - package their secretions and release them via exocytosis
- Holocrine glands - store their secretions and then release the entire contents of the cell
Goblet cell
- Unicellular exocrine gland
- Ductless and composed of modified columnar epithelial cell
- Found among columnar cells pf the respiratory and digestive tracts and the conjunctiva of the eye
- Secretes mucin (mucous)
Classification of exocrine glands
1) Serous secretions:
- Watery
- Contain a high concentration of enzymes
2) Mucous secretions:
- Thick, viscous
- Composed of glycoproteins
- Mixed exocrine glands contain both mucous and serous components
Connective tissue
Functions:
- Supports and connects tissues throughout the body
- Makes up a huge proportion of the tissue within the body
- Falls under 7 broad categories:
1) Areolar (loose)
2) Adipose (loose)
3) Fibrous (dense)
4) Cartilage (dense)
- Forms structural connections between other tissues
- Forms a protective sheath around organs and helps insulate the body
- Acts as a reserve for energy
- Composes the medium that transports substances from one region of the body to another
- Plays a role in the healing process and in control of invading microorganisms
Connective tissue components
1) Ground substance:
- Medium through which cells exchange nutrients and waste within the blood stream
- Amorphous (without shape)
- Ranges in texture - liquid/gel
- Acts to protect the more delicate cells it envelopes
- Serves as an effective obstacle for invading microorganisms
2) Protein fibres (extracellular fibres)
- The majority of connective tissue is made up of these two proteins: Collagen and Elastin
- Collagen - dense, strong, fibrous - found in high quantities in tendons and ligaments
- Elastin - allows stretch and compliance - found in high quantities in skin, blood vessel walls, vocal tissue, lungs
3) Cells (in connective tissue)
- Fixed cells: involved in production and maintenance of the matrix - fibroblasts (collagen/elastin), chrondroblasts (cartilage), osteoblasts (bone), adipocytes (store fat)
- Transient cells - involved in the repair and protection of tissues - leukocytes (WBC’s), mast cells, macrophages
Areolar (loose) connective tissue
- Fibres and cells suspended in a thick, translucent ground substance
- Predominant cell is the fibroblast
- Surrounds every organ; forms the layer that connects skin to muscle; envelopes blood vessels, nerves, and lymph nodes; present in all mucous membranes
Adipose connective tissue
- Areolar tissue in which adipocytes predominate
- Highly vascular
- Acts as an energy storehouse and a thermal insulator (almost unlimited storage)
Dense regular tissue
- Composed of tightly packed, parallel collagen fibres
- Relatively avascular
- Makes up tendons and ligaments
- Can be found in fascial sheets that cover muscle
- Tendons - attach bone to muscle
- Ligaments - attach bone to bone
Dense irregular tissue
- Composed primarily of collagen fibres arranged in thick bundles
- Fibres are interwoven to form a single sheet
- Found in the dermis of the skin and in the fibrous coverings of many organs
- Forms the tough capsule of joints
Dense elastic tissue
- Primarily composed of elastic fibres
- Fibres may be arranged parallel or interwoven patterns with fibroblasts and collagenous fibres interspersed
- Found in spaces between vertebrae and in areas of the body that require stretching (walls of arteries, stomach, bronchi, bladder etc)
Specialised connective tissue
- Cartilage - hyaline, elastic, fibrocartilage
- Bone
- Blood
Cartilage
- Found in joints and in the ear, nose and vocal chords
- Forms a framework on which bone is formed
- No innervation; avascular (no blood supply)
- Cells: Chondrocytes: Cartilage cells, Chrondroblasts develop into chondrocytes
- Matrix: Collagen fibres are most commonly found in the matrix, but elastic fibres are also present in varying amounts
- Hyaline - most common type. Found in between joints and in embryonic skeleton
- Elastic - higher levels of elastin. Found in larynx and pinna
- Fibrocartilage - found in between vertebrae (intravertebral discs)
Mucous membranes
- Line organs with connections to the outside environment (mouth, intestines, nasal passages etc)
- Usually composed of either stratified squamous or simple columnar epithelium covering a layer of loose connective tissue (areolar)
- Produces mucus via goblet cells
