Lecture 34. Tissue Organisation

Question 1

What are tissues composed of?

Answer 1

Cells that have a common embryonic origin – specialised function

Question 2

What influences the structure and properties/functions of tissues?

Answer 2

The cell-cell connections and the surrounding extracellular matrix

Question 3

What is histology?

Answer 3

The study of tissues

Question 4

Embryonic origin of mammalian tissues

Answer 4

Progenitor/precursor cells from embryonic stem cells found in blastocyst

Question 5

Where is epithelia tissue found?

Answer 5

Abundant and widely distributed throughout the body

Question 6

How are epithelial cell arranged?

Answer 6

In tightly packed continuous sheets in single or multiple layers

Question 7

Epithelial cells interactions with surfaces

Answer 7

Line all internal surfaces and cover all external surfaces (forming boundaries of body)

Question 8

Are epithelial cells polarised?

Answer 8

Yes

Question 9

What are the 2 layers that make up the thin extracellular matrix?

Answer 9

Basal lamina and reticular lamina

Question 10

What are the major functions of the epithelia tissue?

Answer 10

1) Protection – Waterproof covering (skin), minimising
environmental influence
2) Selective barriers – controlled movement of substances into
and out of the body
3) Filtration – Kidney glomeruli
4) Secretion – products are released onto their apical surface
5) Absorption – GIT
6) Excretion – Urine formation

Question 11

What are the two types of epithelia tissue?

Answer 11

1) Covering and lining epithelium
2) Glandular epithelium

Question 12

What are the 3 cell shapes epithelial tissues can be made up of?

Answer 12

Squamous, Cuboidal, Columnar

Question 13

Squamous tissue location

Answer 13

Endothelial cells of blood vessels

Question 14

Cuboidal tissue location

Answer 14

Cells of the ovary and kidney tubules

Question 15

Columnar tissue location

Answer 15

Lining of GIT

Question 16

What are the 3 types of cell layers of epithelial tissue

Answer 16

Simple, Pseudostratified, Stratified

Question 17

Simple cell layer

Answer 17

One layer

Question 18

Pseudostratified cell layer

Answer 18

One layer but appears like several

Question 19

Stratified cell layer

Answer 19

> 2 layers

Question 20

Functions of connective tissue

Answer 20

Bind, support, strengthen, protect, insulate and compartmentalise

Question 21

What are the two main elements of connective tissue?

Answer 21

Extracellular Matrix and widely spaced cells

Question 22

What make up the extracellular matrix?

Answer 22

Ground substance – Water and glycosaminoglycans (GAGS) - Gel With the exception of Hyaluronan GAGS are linked to proteins= Proteoglycans
Protein fibres – Collagen (25%), Elastin fibres and Reticular fibres

Question 23

What undifferentiated progenitor cells do loose and dense CT contain?

Answer 23

Fibrobalsts

Question 24

What undifferentiated progenitor cells do cartilage CT contain?

Answer 24

Chondroblasts

Question 25

What undifferentiated progenitor cells do bones contain?

Answer 25

Osteoblasts

Question 26

What is muscle tissue comprised of?

Answer 26

Elongated cells, muscle fibres - myocytes

Question 27

What are the 3 types of muscle tissue

Answer 27

Skeletal, Smooth and Cardiac

Question 28

Functions of muscle tissue

Answer 28

Movement and locomotion Maintenance of posture Controlled movement of substances Thermogenesis

Question 29

Properties of muscle tissue

Answer 29

Electrical excitability Contractility Extensibility Elasticity

Question 30

Skeletal muscle

Answer 30

Long cylindrical fibres Range from a few cm – 30cm in length Striated due to overlapping fibrils of actin and myosin Develop from the fusion of 100s myoblasts – skeletal fibres are multinucleated The number of muscle fibres is set before you are born Each fibre will be innervated by somatic motor neurones (conscious control therefore voluntary activation) Each fibre is closely associated with a capillary Fast speed of contraction

Question 31

Smooth muscle

Answer 31

Short fibres (30 – 200 µm) and tapered at each end Centrally located oval nucleus No overlap of filaments therefore non-striated (smooth) Greater stretch and recoil capacity Slower and longer lasting contraction some are autorhythmic-myogenic

Question 32

What are the two types of smooth muscle?

Answer 32

Visceral and Multiunit

Question 33

Visceral

Answer 33

Skin and some tubular structures e.g. stomach and intestines Several fibres are innervated by one ANS motor neuron synapse. Fibres are connected by many gap junctions – spread action potentials

Question 34

Multiunit

Answer 34

Lung airways, walls of large arteries muscles of the iris Each fibre has one ANS motor neuron synapse Not as closely associated as visceral - much fewer gap junctions

Question 35

Cardiac muscle

Answer 35

Cardiac muscle fibres 50-100 µm long and ~14 µm in diameter Fibres are branched with usually one centrally located nucleus Connected to neighbouring fibres by intercalated discs via desmosomes Many gap junctions are present to allow the myocardium to contract as one coordinated unit Myogenic

Question 36

Which groups of cardiac muscle are autorhytmic?

Answer 36

Pacemaker (SAN) – Under autonomic regulation Conduction system (AVN; Bundle of His; Bundle branches; Purkinje fibres)

Question 37

What are the two cell types of nervous tissue?

Answer 37

Neurons and Neuroglia

Question 38

Neurons

Answer 38

Form complex networks in the brain Electrical excitability Convert stimuli into action potentials – nerve impulses Connect all regions of the body to brain and spinal cord Sensing; thinking; remembering; muscle activity; glandular secretions Long cells Composed of a cell body (organelles); dendrites (receive signals); axon (propagates the signal, some are myelinated)

Question 39

What are the 4 classifications of neurons?

Answer 39

Multipolar Bipolar Unipolar Pyramidal

Question 40

Neuroglia

Answer 40

Do not generate or conduct nerve impulses Smaller but more abundant Provide supporting role to neurons