Connective tissue Flashcards
Are there non-roaming macrophages in connective tissue?
Yse, these are fixed macrophages and are permanent residents of their tissues
Where is trabecular bone found?
In the interior of some bones and at the end of long bones
How are blood and lymph fluid connective tissues?
Cells circulate in a liquid extracellular matrix containing nutrients, salts, and wastes
Give two examples of dense connective tissue
Regular elastic and irregular elastic
What do ‘free’ macrophages do in connective tissue?
Move rapidly through the matrix engulfing infectious agents and cellular debris
Which has a greater resistance to stretching, loose or dense connective tissue?
Dense connective tissue
What would bones be like without the inorganic phase (mineral crystals)?
Able to flex, provide little support
What are adipocytes?
Cells that store lipids as droplets that fill most of the cytoplasm
Fibroblasts and adipocytes are ____ cells
Fixed
Which fibres are the most numerous?
Collagenous
Specialised connective tissues include which two tissue types?
Supportive and fluid connective tissues
What does ‘fixed cells’ mean?
The cells remain within the connective tissue
What is the effect of bone having organic and inorganic phases?
The combination makes bone hard and flexible at the same time
The function of a particular connective tissue correlates with the amount of what things in that tissue?
Cells, ground substance, and fibres
____ stem cells are commonly found in connective tissues
Mesenchymal
Give three examples of loose connective tissue
Areolar, adipose, and reticular
How do adipocytes apprear in stained sections?
Large white circular cells
What type of stain readily blackens reticular fibres?
Silver stains
Name a type of wandering cell that enters connective tissues (aside from macrophages)
Lymphocytes
Bone contains a relatively small number of ____ entrenched in a matrix of ____ fibres
Cells; collagenous
A few distinct ____ types and ____ packed fibres in a matrix characterise supportive connective tissue
Cell; densely
What makes fibrocartilage tough?
Thick bundles of collagenous fibres dispersed through its matrix
Elastic fibres contain which protein?
Elastin
What are the subcategories of connective tissue proper?
Loose connective tissue and dense onnective tissue
How many main types of fibres are secreted by fibroblasts?
Three
What are the major categories of dense connective tissue?
Regular and irregular connective tissue
Which is heavier, trabecular or cortical bone?
Trabecular
What is the name of the process of bone formation with the cartilage template of the embryonic skeleton?
Endochondral ossification
Reticular tissue is a mesh-like supportive framework for soft organs such as ____ tissue, ____, and ____
Lymphatic; spleen; liver
Describe fluid connective tissue
Various specialised cells circulating in a watery fluid containing salts, nutrients, and dissolved proteins
How do reticular fibres appear in a haemotoxylin and eosin (H&E) stain?
Reticular fibres are poorly visualised by H&E stains
Why might cortical bone be so dense?
So it can withstand compressive forces
Name two major forms of supportive connective tissue that allow the body to maintain its posture and protect internal organs
Cartilage and bone
What gives cartilagenous tissue its distinctive appearance?
A large component of solid ground substance
Collagenous fibres appear wavy under photomicrograph - what can straighten this out?
Tension on the tissue
____ fibres hold connective tissues together, even during body movement
Collagenous
What is ground substance made of?
Carbohydrates and proteins
Ground substance is secreted by ____
Fibroblasts
What forms can ground substance be found in?
Fluid or mineralised and solid (as in bones)
What type of tissue is the most widely distributed primary tissue in the body?
Connective tissue
Which subtype of bone is more solid and has greater structural strength?
Cortical bone
Areolar tissue shows little ____
Specialisation
When do salt crystals form in bone?
When calcium phosphate and calcium carbonate combine to create hydroxyapatite
What are migratory or wandering cells?
Cells that move in and out of connective tissue in response to chemical signals
What are the categories of connective tissue?
Connective tissue proper, supportive connective tissue, and fluid connective tissue
Name some functions of lymphocytes in connective tissue proper
Phagocytosis, allergic or inflammatory reactions, and immune defence
Name the three main types of fibres secreted by fibroblasts
Collagenous fibres, reticular fibres, and elastic fibres
What identifies an adipocyte?
The large lipid droplet that occupies the majority of the cell and pushes the nucleus to the periphery of the cell in an accentric and flattened position
What is the term for blood cell production?
Haematopoesis
In typical histological preparations, amorphous ground substance appears as what?
Clear spaces between the fibres and cells as it usually dissolves out of the tissue section during preparation
How is areolar tissue distributed?
In a random, web-like fashion
Dense regular connective tissue fibres are ____ to each other
Parallel
Is bone vascular?
Yes, highly vascular
Describe the arrangement of fibres in loose connective tissue
Loosely organised, leaving large spaces in between
What allows continued bone growth until adulthood?
A plate of hyaline cartilage at the ends of bone
What are some features of collagenous fibres?
Flexible, has great tensile strength, and resist stretching
Which has more collagenous fibres, loose or dense connective tissue?
Dense connective tissue
What the term for cells that move in and out of connective tissue in response to chemical signals?
Migratory or wandering cells
Ground substance is usually a ____
Fluid
Why does fibrocartilage have such a high fibrillar content?
This allows it to resist high compressive forces while still retaining its firm support
What is a macrophage derived from?
A monocyte
Most bones contain a combination of ____ and ____ bone tissue
Cortical; trabecular
What is articular cartilage?
Hyaline cartilage that covers bones were they articulate to form moveable joints
What are the main types of cartilagenous tissue?
Hyaline cartilage, fibrocartilage, and elastic cartilage
What characterises connective tissues?
Their abundance of intercellular material and relatively few cells
Collagenous fibres in bone are embedded in what?
Mineralised ground substance
What is the function of reticular fibres in the reticular tissues of soft organs?
They anchor and provide structural support to the parenchyma
Describe inactive/resting fibroblasts
Reduced cytoplasm and small, flattened, and elongated nuclei
What is the ‘parachyma’?
The functional cells, vessels, and nerves of an organ as separate from the surrounding and supporting connective tissues
In ligaments, not all fibres are ____
Parallel
Elastic cartilagenous tissue contains ____ fibres, ____ fibres, and ground substance
Elastic; ground
Do elastic fibres branch?
Yes
What is the major function of connective tissue?
To support and connect tissues and organs
How can lymphocytes be recognised in connective tissue proper?
Lymphocytes have a large round nucleus that occupies almost all the cytoplasm of the cell
Which cell is predominant in adipose tissue?
Adipocytes
How does trabecular bone appear under the microscope?
As a sponge, with empty spaces between trabeculae or ‘little beams’ of bone tissue
What kind of areas is fibrocartilage found?
Areas of high loading and stress
Hyaline cartilagenous tissue consists of ____ and ____ collagenous fibres and ground substance
Short; dispersed
List some locations areolar tissue can be found. There are four possible answers.
Superficial fascia (hypodermis of the skin, fills the spaces between muscle fibres, surrounds blood and lymph vessels, and supports organs in the abdominal cavity
Name three fixed cells in connective tissue proper
Fibrocytes, adipocytes, and mesenchymal cells
What is involved in the organic phase of bone tissue?
Fibres, amorphous ground substance, cells
Ligaments and tendons are made of which type of connective tissue?
Dense regular connective tissue
What is the most common type of cartilage in the body?
Hyaline cartilagenous tissue
What can mesenchymal stem cells differentiate into?
Mature cells such as adipocytes, fibroblasts, and specialised connective tissue cells including bone and cartilagenous cells
The matrix of connective tissue usually includes a large amount of ____ ____
Extracellular material
What is a feature of dense connective tissue?
It is reinforced by bundles of fibres that provide tensile strength, elasticity, and protection
Is cartilagenous tissue vascular?
No, which is why all nutrients need to diffuse through the matrix to reach the chondrocytes
Which type of fibre is formed from the same protein subunits as collagen?
Reticular fibres
How do elastic fibres appear in H&E sections?
Most elastic fibres are too thin to be seen in H&E sections
What are the common three components of connective tissues?
Cells, large amounts of amorphous ground substance, and fibres
Areolar tissue underlies most ____
Epithelia
What is the function of fibroblasts?
Secrete polysaccharides and proteins which combine with extraellular fluids to produce a viscous ground substance that with embedded fibrous proteins forms the extracellular matrix
What are the two types of intercellular substances?
Amorphous ground substances and fibres
Both ____ and ____ connective tissue have a variety of cell types and protein fibres suspended in a viscous ground substance
Loose; dense
Name three examples of fibrocartilage
Menisci in the knee, pubic symphysis, and intervertebral discs
Describe the difference in arrangement of cells between epithelial and connective tissue
Epithelial tissue is usually composed of cells closely packed with little or no extracellular space in-between; connective tissue cells are dispersed in a matrix
Mesenchymal stem cells are commonly found in what kind of tissue?
Connective tissues
Give two examples of bone supportive connective tissue
Compant bone, cancellous bone
Give some examples of dense irregular connective tissue that’s rich in collagenous fibres. There are four possible answers
The dermis of the skin, fibrous capsules of some organs, periosteum, endosteum, and deep fascia
Give three examples of cartilage supportive connective tissue
Hyaline, fibrocartilage, and elastic
Why is the matrix of bone described as ‘calcified’?
Calcium salt deposits
What would bones be like without the organic phase?
Brittle and easily shattered
List the locations hyaline cartilage can be found. There six possible answers
In the ribcage as the costal cartilages
Trachea
Bronchial tree
Most laryngeal cartilages (thyroid and cricoid)
In the nose
Covers bones where they articulate to form moveable joints (articular cartilage)
What does hydroxyapatite incorporate as it crystallises on the collagenous fibres?
Other inorganic salts like magnesium hydroxide, fluoride, and sulphate
What is the appearance of collagenous fibres in photomicrographs?
Wavy, ‘crimped’
How do collagenous fibres appear in haemotoxylin and eosin (H&E) stained tissue sections?
Pink unbranching fibres, 1-12μm in diameter
What is the direction of the fibres in dense irregular connective tissue?
Random
What is the function of loose connective tissue located between organs?
It acts to absorb shock and bind tissues together
Which fibres generally occur in bundles?
Collagenous
What is the most common form of loose connective tissue?
Areolar tissue
What is the basic function of bone?
To provide protection to internal organs and support the body, as well as functions in Ca homeostasis and haematopoesis within bone marrow
Supportive and fluid connective tissues are collectively referred to as what?
Specialised connective tissues
Which types of cells are found in areolar tissue?
Fibroblasts, adipocytes, macrophages
Which are thinner, elastic or collagen fibres?
Elastic
Give two examples of fluid connective tissue
Lymph and blood
How do hyaline cartilage samples appear under the microscope?
Clear due to the cartilagenous fibres being so thin (‘hyalos’ means ‘glass-like’)
Silver stains make fibres appear ____
Black
Is bone fast or slow to heal?
Fast
Describe the structure of fibroblasts
Spindle-shaped cells with moderate amounts of cytoplasm and a large oval nucleus when active
What is involved in the inorganic phase of bone tissue?
Minerals
What is the most abundant cell in connective issue proper?
Fibroblast
Where are reticular fibres most abundant?
In the reticular tissue of soft organs such as the liver or spleen
What is the approximate diameter of elastic fibres?
0.2 - 1 μm
How are connective tissue cells arranged?
In a matrix
Cartilage and bone are what type of connective tissue?
Supportive connective tissue
The matrix of bone is described as ____ due to the deposited calcium salts
Calcified
Name three locations where elastic fibres are prominent
Skin, arteries, elastic ligaments of the vertebral column
What is the effect of dense regular connective tissue fibres being parallel to each other?
It enhances tensile strength and resistance to stretching in the direction of the fibre orientation
What is the most significant property of elastin?
It returns to its original shape after being stretched or compressed
Why is bone faster to heal than cartilage?
Bone is highly vascular
What is the name of the plates of hyaline cartilage at the ends of bone that allow bone growth until adulthood?
Epiphyseal growth plate
Why are cartilagenous tissues slow to heal?
They are avascular, so all nutrients must diffuse through the matrix to reach the chondrocytes
What are the structural differences between collagenous and reticular fibres?
Reticular fibres remain narrow and are arranged in a branching network that has a net-like framework
What are the two subtypes of bone?
Trabecular and cortical bone
What characteristic of bone tissure is unique to only that subtype?
It has a biphasic composition - an organic phase comprising 1/3 tissue and inorganic phase comprising 2/3 tissue
Does trabecular bone support loading from one or multiple directions?
Multiple
Macrophages enter the connective tissue matrix from the ____ ____
Blood vessels
Which type of fibres are readily blackened by silver stains?
Reticular fibres
What is the advantage of the random direction of fibres in dense irregular connective tissue?
The arrangement gives the tissue greater strength in all directions and less strength in one particular direction
The rigid extracellular matrix of bone contains mostly ____ fibres embedded in mineralised ground substance
Collagenous
Which cartilage forms the template of the majority of the embryonic skeleton before bone formation begins?
Hyaline cartilage
What is the major component of connective tissue matrix?
Ground substance, often criss-crossed by fibres
Name the three categories of connective tissue
Connective tissue proper (AKA general connective tissue), supportive connective tissue, and fluid connective tissue
Ligaments have a higher proportion of ____ fibres than tendons
Elastic
Where does haematopeosis occur?
Within the bone marrow compartment
Which type of tissue is characterised by a relative abundance of cells and ground substance and a loose arrangement of fibres?
Loose connective tissue
How do some dense irregular connective tissues achieve stretching in several directions?
By alternating layers where fibres run in the same orientation in each layer, and the layers themselves are stacked at an angle
What is the purpose of supportive connective tissue?
To provide structure and strength to the body and protect soft tissues
____ tissue represents the connective tissue component of epithelial membranes
Areolar
Areolar tissue is the most common form of what category of connective tissue?
Loose connective tissue
The ground substance in bone is ____
Mineralised
Which type of tissue is characterised by the close packing of fibres, relatively few cells, and little ground substance?
Dense connective tissue
What does the matrix of collagenous fibres in bone provide?
It provides a surface for inorganic salt crystals to adhere
Most ____ fibres are too thin to be seen in H&E sections
Elastic
Give two examples of supportive connective tissue
Bone and cartilage
Collagenous fibres give ____ and ____ their characteristic resilience and strength
Ligaments and tendons
Which fibres are the most widely distributed?
Collagenous
The amount of cells, ground substance, and fibres in connective tissue correlates with the ____ of that tissue
Function
Which type of cell produces the reticular fibres that form the network onto which other cells attach?
Fibroblasts
Name three types of cells found in connective tissue that are part of the immune system
Macrophages, leukocytes, and phagocytic cells
Where does the extracellular material in a connective tissue matrix coe from?
It is produced by the connective tissue cells that are embedded within it
What is the best stain to view elastic fibres?
Selective silver stains, where fibres appear black
What are collagenous fibres made of?
Fibrous protein subunits called collagen linked together to form a long and straight fibre
The surface of hyaline cartilage is ____
Smooth
Name three locations where elastic cartilaginous tissue is found
The auricle of the ear, the Eustachian tube, and the epiglottis of the larynx
What are specialised connective tissues?
The overarching term for supportive and fluid connective tissues
