tissues Flashcards
2 Epithelia types
Covering and lining
Glandular
Characteristics of epithelial tissue
apical-basal polarity - apex for transport mechanisms etc
base basement membrane - hemi-desmosomes secure cells to basement membrane. Provides additional barrier. basal lamina,(2 layers) lamina reticularis (collagen fibres
High regenerative
ability limited by contact inhibition
When junctions are removed by damage, cells proliferate via mitosis. Gives high risk of malignancy as uncontrolled proliferation breaking through basement membrane - metastasise through connective tissue. Some are prone to over granulation
Types of epithelial junctions
Tight junctions prevent passage of proteins and maintain apical-basal polarity
Adherens junctions maintain cell to cell contact
Desmosomes resist shearing forces and stress can unzip for motility and growth
Hemi desmosomes as before
Gap junctions channels between cells to allow solutes to pass to flow between cells
Epithelial tissue is avascular and innervated. What does that mean?
It is supplied by nerves but does not have blood vessels
Solutes diffuse from blood vessels within the underlying connective tissue
Classification epithelial tissue by shape
Squamous - flat slabs -
Cuboidal - rounded nuclei
Columnar - tall with oval nuclei often have cilia
simple epithelia layers
single cell layer on basement membrane, endothelium lining blood and lymph vessels
stratified epithelia layers
layers of cells are stacked on top of basement
membrane (forms border of dermis)
epidermis becomes cornified (keratinised) for protection
Vascular endothelium
Endothelium differentiates vascular and lymphatic lining epithelium
tunica intima - simple squamous
Endothelial cells are in contact with blood supply
Permeability via spaces between the squamous endothelial cells can be regluated by cell contraction ad relaxation
Functions of epithelia
Protection eg skin, mucosa
Absorption eg lining of digestive tract
Filtration and excretion eg kidneys
Secretion glandular
what are pores in endothelial cells called?
Fenestrations
what is sinusoidal endothelium? what does it allow?
It is an incomplete basement membrane and allows Transcytosis ( endo and exocytosis
what are enterocytes and what do they line and form?
Simple columnar epithelium
lines the ileum and colon
along with basement membrane it forms the villi (absorption) in the ileum and crypts (secretory) ileum and colon
enterocytes are joined together by what junctions?
selectively permeable tight junctions to allow passage of Na+ and water into the crypts
what do villious enterocytes absorb?
water and electrolytes
carbs as monosaccharides
proteins as small peptides and amino acids
fat as monoglyceride and free flatty acids these are transported from the basal side into hepatic portal veins or lymph in the case of fat for processing or storage in liver
what are 80% of the liver cells called?
hepatocytes - highly regenerative
what do hepatocytes do?
many metabolic, endocrine and secretory functions which include the metabolism and regulation of carbs, lipids and proteins
through what vein do hepatocytes receive blood and where does it enter?
recieves blood from the GI tract via the hepatic portal vein and this enters sinusoids within the liver lobules which then enters the central veins to retuns to the heart via inferior vena cava
2 types of connective tissue
Proper (cartilage and membrane that bind, dermis, adipose specialised - bone, cartilage, blood
which cells form the extracellular matrix?
Fibroblasts (healing) secrete collagen
Chondroblasts secrete cartilage
Osteoblasts secrete bone
..blasts are?
immature cells or cells that produce tissue components
…cytes are?
mature cells
Blood components
Fluid matrix Plasma (90% water) and 10% proteins, electrolytes, hormones, O2, glucose
Formed elements Erythrocytes rbc 48/54 billion
leukocytes wbc 7.5 million/ml neutrophils, monocytes, lymphocytes, mast cells eosinophils, basophils
platelets (thrombocytes)
2 types of nervous tissue and what do they form?
neurons
support cells form
the CNS - spinal cord and brain
peripheral nervous system (PNS) the spinal nerves and branches
afferent neurons do what?
conduct action potentials towards the CNS eg sensory neurons
what do efferent neurons do?/
conduct action potential away (exit from CNS)form the CNS eg motor neurons
myelinated slow or fast?
fast action potential conduction
unmyelinated slow or fast?
slower action potential conduction
within the CNS neurons form?
grey matter - somata (cell bodies) and synapses
white matter - myelinated axons following tracts
all afferent and efferent neurons are bundled into nerves where?
the PNS
what do nervous tissue support cells do? name 2 types
they are non-conductive and support insulate and protect the neurons
what do schwann cells do?
Schwann cells secrete myelin sheath around myelinated PNS neurons
name 2 types of Glial cells and what do they do?
Microglia are macrophages in the brain and spinal cord
Astrocytes help to create the blood-brain barrier and have many other functions
the passage of solutes in and out of the blood brain barrier is regulated by?
tight junctions between endothelial cells
Pericytes that can expand and contract to regulate permeability
a basement membrane that surrounds the endothelial cells and pericytes
astrocytes ‘feet’
3 types of muscle tissue
skeletal - VOLUNTARY striated myocytes with sarcomeres efferent neurons carry action potentials away from CNS allows movement of body and respiratory muscles
smooth in walls of hollow organs non striated myocytes in sheets with gap junctions blood vessels bronchi involuntary autonomic nervous system and other ligands (histamine, angiotension2 etc)
cardiac forms myocardium faintly striated myocytes with sarcomeres and gap junctions
Involuntary stimulated by autorhythmic cells in the Sinoatrial node and regulated by ANS
what do you know about smooth muscle
long, tapered myocytes arranged in sheets
found in walls of hollow organs bronchi and vessel
not striated because actin and myosin filaments are not arranged in sarcomeres. They are anchored by dense bodies which cause contraction in a twisting manner
contraction is syncytial (sync all at same time)due to flow of cation though gap junctions. Na+ and Ca+ pass from myocyte to myocyte and contraction is slow
what do you know about cardiac muscle?
joined by intercalated discs. Cardiomyocytes have gap junctions and contract syncytially. have saracomeres like skeletal but not lined up because of the branching of cardio myocytes from myocardium so striation appears faint
