Week 5: Introduction to Tissues of the Body Flashcards
Define a tissue.
A tissue is defined as a group of cells and intracellular materials with a specific organisation that work together to carry out one or more specific functions.
What are the four primary (basic) tissues of the human body?
All tissues in the body fall into one of four basic subtypes:
1. Epithelial: lines the surfaces of the body and organs, forming a protective barrier. Can also form glands.
2. Connective: underlies and provides support and structure to the body
3. Muscle: responsible for movement, both voluntary and involuntary
4. Nervous: specialised for transmitting and processing information in the body
What are organs composed of?
Tissues are the building blocks of organs and are composed of cells that have a similar morphology, physiology, and function.
How can the four basic tissue types be defined?
Each of the four basic tissue types can be defined according to:
- Morphological characteristics and location
- Functional properties
What tissues are defined according to morphological characteristics and location?
Epithelium (shape of cells, number of cell layers, specialisations at tissue surface) and connective tissue (types of cells, type and arrangement of fibres [extracellular material], relative proportions of cells, fibres and AGS).
What tissues are defined according to functional properties?
Muscle (ability of cells to contract [movement] and contractile proteins [actin and myosin]) and nervous tissue (ability to receive, transmit and integrate electrical impulses, non-excitable support cells [neuroglia]).
What are the characteristics of epithelium?
- Highly cellular with little intracellular material: closely packed forming a barrier or lining on surfaces
- Often forms sheets or layers
- Tissue layer has one free surface (not in contact with another tissue and is instead in contact with the cavity/ space)
- Cells attached to and supported by a basal lamina/ basement membrane (on the opposite side of free side). This separates epithelium from CT (and other basic tissue types)
- Avascular, meaning it contains no blood vessels (obtains supply of oxygen and other nutrients from adjacent tissues, e.g., CT)
- Dynamic, meaning cells are constantly shed and replaced (high turnover rate and regenerative capacity compared to other tissue types)
- Have various functions including protection, absorption, secretion and sensory reception
Where is epithelial tissue found?
Can be found on the outer layer of the skin, lining internal organs, lining the cavities and passages of the body, and in glands.
Where is surface epithelium found?
Surface epithelium covers all natural surfaces and lines all natural cavities of the body.
What is glandular epithelium? Where is it found?
Glandular epithelium contains cells that produce a secretion. Can either be in glands: endocrine (no ducts, secrete hormones into blood) or exocrine (secrete onto a surface, have ducts), or exist as single cells in in surface epithelium.
What are the types of glands?
Exocrine glands secrete onto a surface and have ducts. Endocrine glands have no ducts and secrete hormones into blood.
Unicellular glands exist in surface epithelium.
How is epithelium classified?
By shape (squamous, cuboidal, columnar), by arrangement (simple, stratified, pseudostratified), by keratinisation (keratinised, non-keratinised)
What are the characteristics of CT?
- Most abundant and morphologically the most diverse of all the primary tissues
- Composed of a wide range of cell types and have abundant ECM (fibres and AGS). Fibres in CT are collagen, elastic and reticular fibres
- Has few cells, compared to epithelial tissue
- Highly vascular: contains blood vessels and nerves
Can be found in bone, cartilage, blood and loose or dense CTs - Function in support, protection and connection of structures
How is CT classified?
By number of cells (dense or loose), by arrangement of fibres (regular or irregular), by type of extracellular material and fibres (collagen, elastic, reticular fibres)
What are the characteristics of muscle tissue?
- Cells are elongated and hence called muscle fibres. These contain specialised proteins called actin and myosin
- Blood supply housed in CT between muscle fibres (avascular)
Tissue types separated by a basal lamina, which is found at the boundary - Function in movement and contraction: capable of shortening in length and returning to a resting state, generating physical force and thus movement
How can connective tissues be classified?
By sub-type (skeletal, cardiac, smooth). By structure (striated, non-striated). By function (voluntary, involuntary)
What are the sub-types of muscle tissue?
Skeletal, smooth and cardiac
What are the main features of skeletal muscle?
- Fibres: striated, tubular and multi-nucleated
- Voluntary
- Usually attached to skeleton
What are the main features of smooth muscle?
- Fibres: non-striated, spindle-shaped, and uni-nucleated
- Involuntary
- Usually covering wall of internal organs
What are the main features of cardiac muscle?
- Fibres: striated, branched and uni-nucleated
- Involuntary
- Only covering walls of the heart
What are the characteristics of nervous tissue?
- Composed of neurons (nerve cells) and glial cells. Nerve cells are composed of a cell body (soma - where the nucleus is), and a long cytoplasmic process (axons - single branched, and dendrites - numerous branch)
- Various specialised supporting cells (neuroglia in CNS)
- PNS neuroglia: Schwann cells, satellite cells
- Can be found in the brain, spinal cord and peripheral nerves
- Function in transmitting and processing information
What is derived from the ectoderm during embryologic development?
Ectoderm = external layer.
Nervous tissue and epithelium
What is derived from the mesoderm during embryologic development?
Mesoderm = middle layer
Connective tissue, muscle and epithelium
What is derived from the endoderm during embryologic development?
Endoderm = internal layer
Epithelium
Which embryonic layer is epithelium derived from?
All 3; ectoderm, mesoderm and endoderm
Which embryonic layer is connective tissue derived from?
Mesoderm
Which embryonic layer is nervous tissue derived from?
Ectoderm
Which embryonic layer is muscle tissue derived from?
Mesoderm
What are tissue membranes? Where are they found?
Tissue membranes are a functional unit composed of a surface epithlium and its underlying (loose) CT. It covers the surface of the body, or lines a naturally occurring cavity within the body, or covers the outer surface of an organ directly abutting the body cavity.
Give examples of types of tissue membrane.
Mucosa/ mucous membrane, serosa/ serous membrane, synovial membrane
What is a mucosa/ mucous membrane?
An epithelial membrane that lines cavities connected to the outside (it is continuous to the outside). Consists of surface epithelium, basement membrane, supporting CT, and smooth muscle (can include glands)
What is serosa/ serous membranes?
An Epithelial membrane that lines internal body cavities. Consists of mesothelium, basement membrane and supporting CT
What is the synovial membrane? Where is it found? What is its function?
A CT membrane that only contains specialised CT, and no epithelium. It lines capsules of synovial joints, producing a lubricating and nutritive synovial fluid.
What is the level of organisation in the human body?
cells –> tissues –> organs –>organ systems –> human body
