Lecture 4 - Basic tissues

Question 1

Epithelia: what is it, where is it located, and what are its important characteristics?

Answer 1

Loosely-packed cells supported by a basement membrane

Cover surfaces, line cavities, and tubules, and form glands

Has avascularity (few or no blood vessels), good regeneration, polarity (apical, basal), apical always faces out of the body or into a lumen while basolateral faces the internal body

Question 2

How many layers is simple epithelium?

Answer 2

One

Question 3

How many layers can stratified epithelium be?

Answer 3

Two or more

Question 4

Squamous, cuboidal, columnal (in terms of shape)

Answer 4

Flat, cuboidal, and rectangular

Question 5

Types of epithelia (6)

Answer 5

• Simple squamous,
• Keratinised stratified squamous,
• Non-keratinized stratified squamous,
• Simple cuboidal,
• Simple columnal,
• Pseudostratified stratified columnar with goblet cells .

Question 6

Keratinized stratified epithelia: what is it, what does it do, where is it mostly present?

Answer 6

Many layers of flat cells with oval-shaped nuclei containing keratin

Specially structured to be waterproof and reduce evaporation from underlying tissues

Epidermis (external skin)

Question 7

Pseudostratified ciliated columnar with goblet cells: what is it, what does it do, where is it mainly found, and any special characteristics?

Answer 7

Columnar cells seemingly structured in layers, but are in fact all connected to one basement membrane.

Mucociliary escalator

Trachea and large airways

Contain goblet cells (secrete mucus and mainly mucin glycoproteins) and cilia (slender, microscopic, hair-like structures or organelles that extend from the surface of some cells).

Question 8

Goblet cells: what are they, where are they mainly found, and what is their main function?

Answer 8

A type of intestinal mucosal epithelial cell, which serves as the primary site for nutrient digestion and mucosal absorption.

They are mainly found throughout digestion system, as well as the nose and throat

The primary function of goblet cells is to synthesize and secrete mucus. As the primary secretory cell in the superficial epithelium of large airways, goblet cells secrete mucin glycoproteins, the major macromolecular components of mucus.

Question 9

Simple squamous epithelium: what is it, what does it do, and where is it mainly found?

Answer 9

One layer of flat cells with oval-shaped nuclei

Exchange of material: gases and nutrients

Blood vessels and alveoli

Question 10

Non-keratinised stratified squamous epithelium: what is it, what does it do, and where is it mainly found?

Answer 10

Many layers of flat cells with oval-shaped nuclei not containing keratin

Protection / forming a barrier

Oral cavity, oesophagus

Question 11

Simple cuboidal epithelium: what is it, what does it do, and where is it mainly found?

Answer 11

One layer of square cells with round-shaped nuclei

Secretion and absorption

Glands and kidney tubules

Question 12

Simple columnar epithelium: what is it, what does it do, where is it mainly found, and any special characteristics?

Answer 12

One layer of rectangular cells with oval-shaped nuclei located basally

Secretion and absorption

Gastrointestinal tract

Contain microvilli

Question 13

Intercellular junctions: what are they and what are their examples?

Answer 13

Things that bind cells together

Desmosomes, hemidesmosomes, tight junctions, and gap junctions

Question 14

Desmosomes: what are they, what are they made of, and what do they do?

Answer 14

Very strong connections between adjacent cells,

Desmoplakin and other proteins

Resist stretching and twisting

Question 15

Hemidesmosomes: what are they, what are they made of, and what do they do?

Answer 15

Attach cells to the base membrane

Several membrane-spanning proteins

Acts as an anchor to the underlying tissue and stabilises the cell’s position

Question 16

Tight junctions: what are they and where are they, what are they made from, and what do they do?

Answer 16

Interlocking proteins that bind cells together near the apical edge

Transmembrane proteins and cytoplasmic scaffolding proteins

Prevent the passage of water and solutes between cells

Question 17

Gap junctions: what are they, what do they do, and what are they made of?

Answer 17

Interlocking membrane proteins containing a central pore, binding cells together and allowing the movements of small molecules and ions (mainly found in cardiac muscle)

Channel proteins: connexions (vertebrates) and innexins (invertebrates)

Question 18

Connective tissue: its functions

Answer 18

• Forms a structural framework for the body
• Supports, surrounds and interconnects other tissue types
• Protects delicate organs
• Transports fluids and dissolved materials
• Stores energy reserves
• Defends body from microorganisms

Question 19

Connective tissue: what cells are present, what does the EM consist of, and what are the types?

Answer 19

An extracellular matrix surrounding cells, including mainly fibroblasts, adipocytes, macrophage, and mast cells

Consists of the ground substance, tissue (extracellular) fluid, and fibres; collagen, reticular & elastic

The two types of CT are specialised connective tissue and connective tissue proper

Question 20

Fibroblasts

Answer 20

Secrete collagen proteins that help maintain the structural framework of tissues.

Question 21

Adipocytes

Answer 21

Acts as a calorie storage system accepting chemical energy in the form of glucose and fatty acid from the blood and converting these metabolites to trigylcerides for storage during fed conditions via lipogenesis.

Question 22

Macrophages

Answer 22

Specialised white blood cells involved in the detection, phagocytosis and destruction of bacteria and other harmful organisms. In addition, they can also present antigens to T cells and initiate inflammation by releasing molecules (known as cytokines) that activate other cells.

Question 23

Mast cells

Answer 23

Play an important role in innate and adaptive immunity. Mast cells recognize harmful antigens by binding to pathogens directly or associating with Pathogen-Associated Molecular Patterns (PAMPs) on the mast cell surface

Question 24

Specialised connective tissue: the three types

Answer 24

Bones, blood, and cartilage

Question 25

Connective tissue proper: the three types

Answer 25

Loose areolar, dense regular, and dense irregular

Question 26

Loose areolar: what is it, what does it do, what does it contain, and where can you find it?

Answer 26

Cellular connective tissue with thin and relatively sparse collagen fibers

Loose connective tissue works to hold organs in place

Contains lots of ground substance, few fibres (collagen & elastic), and a variety of cells: fibroblasts, adipocytes, and macrophages (transient)

Found under the epithelium that covers and lines the body surfaces

Question 27

Dense irregular: what does it do, how does it do it, what does it contain, and where can you find it?

Answer 27

Provides strength to the skin,

Resists tearing by excessive stretching and distension

Little ground substance, many collagen fibre bundles arranged haphazardly, few cells (mainly fibroblasts)

Found in the dermis

Question 28

Dense regular: what is it, what does it do, what does it contain, and where can you find it?

Answer 28

White, flexible tissue that contains tightly packed bundles of collagen fibres running in one direction, arranged parallel to the direction of forces exerted on the particular body part where the tissue is located.

Connects bones to things and transfers forces to the bones

Contains little ground substance, many densely packed bundles of collagen fibres arranged in parallel rows, and few cells (mainly fibroblasts)

Found in tendons and ligaments

Question 29

Ground substance: what is it in connective tissue?

Answer 29

An amorphous gelatinous material. It is transparent, colourless, and fills the spaces between fibres and cells. It actually consists of water and large molecules (glycosaminoglycans (GAGs)) which link together to form even larger molecules called proteoglycans.

Question 30

Dermis: what is it, where is it located?

Answer 30

It’s a fibrous structure composed of collagen, elastic tissue, and other extracellular components that include vasculature (vessels and lymph), nerve endings, hair follicles, and glands.

It’s sandwiched between the epidermis and subcutaneous tissue.

Question 31

Subcutaneous tissue: what is it where is it located

Answer 31

It is the deepest skin layer, composed of fat cells, collagen, blood vessels, and nerves

Located underneath the dermis and is the third layer of the skin.

Question 32

Three types of muscle tissue and their similarities

Answer 32

Skeletal, smooth, cardiac

Elongated parallel to the axis of contraction, contain many mitochondria and contains contractile elements

Question 33

Skeletal muscle: what does it do and where is it found, any key features, and what nervous system affects it?

Answer 33

Moves and stabilises the skeleton, also involved in respiration

Attached to bones and forms sphincters (a ring of muscle surrounding and serving to guard or close an opening or tube) in digestive and urinary tracts.

Long and cylindrical, multi-nucleated, and striated

Somatic nervous system

Question 34

Smooth muscle: what does it do and where is it found, any key features, and what nervous system affects it?

Answer 34

Gastrointestinal movement (peristalsis), alters the diameter of airways and blood vessels

Walls of organs, blood vessels, and airways

Short, fusiform (tapering at both ends; spindle-shaped) cells with one centrally located nucleus, non-striated

Autonomic nervous system

Question 35

Cardiac muscle: what does it do and where is it found, any key features, and what nervous system affects it?

Answer 35

Helps to circulate blood and maintain blood pressure

Located in the heart wall

Branched, striated muscle fibres with the cells having intercalated discs with each having one to two central nuclei

Autonomic nervous system

Question 36

Intercalated discs: what are they, what do they do, and what is their function?

Answer 36

Part of the cardiac muscle sarcolemma

Contain gap junctions for depolarization between muscle fibres and desmosomes that hold the fibres together during cardiac muscle contraction

Ensures the cardiac muscle work as a single unit