Transitional epithelium
The bladder is lined by an elastic stratified epithelium with cells that change shape according to the volume of urine currently stored. When the bladder is full, the pressure exerted by the urine compresses this tissue and the cells take on a thin, flat, squamous appearance (Figure 1.8G2). As the bladder empties, the cells become progressively less compressed, gradually adopting a cuboidal and then a columnar appearance (Figure 1.8G1).
Prokaryotic cells
Cells which contain their DNA within a nuclear membrane are referred to as eukaryotic cells. The cells which make up the bodies of animals (including humans), plants and fungi are all eukaryotic. Human erythrocytes (red blood cells) lose their nucleus as they mature; this loss of the nucleus allows more haemoglobin molecules to be packed into the cell, improving the efficiency of oxygen transport. However, since erythrocytes are derived from nucleated cells, they are still eukaryotic in origin.
Unlike eukaryotic cells, bacterial cells do not have their DNA enclosed within a nuclear envelope and are referred to as prokaryotic cells.
Figure 1.9 Structure of prokaryotic cells
Prokaryotic cells typically have other differences from eukaryotic cells; most are surrounded by a thick, robust cell wall which allows them to survive in fluctuating environmental extremes of temperature, pH and dryness (Figure 1.9). A key feature of bacteria is that they are able to replicate incredibly fast. This allows huge populations to be generated in relatively short periods of time; in the human body this can have disastrous consequences, particularly if bacteria gain access to the blood.
Sepsis is often defined as an overwhelming life-threatening infection. It is more common than myocardial infarction (heart attack) and kills more people in the UK than breast, bowel and prostate cancer combined. Sepsis is more common in the very old and very young whose immune systems are in decline or not fully developed, while patients on immunosuppressive medications such as certain steroids are also at increased risk (Knight and Hore, 2018).
Symptoms of sepsis vary according to the age of the patient. According to the UK Sepsis Trust, the signs of sepsis in an adult include:
1 ‘Slurred’ speech or confusion
2 Extreme shivering or muscle pain
3 Passing no urine (in a day)
4 Severe breathlessness
5 It feels like you’re going to die
6 Skin mottled or discoloured.
In children, sepsis should be suspected if the child:
1 Is breathing very fast
2 Has a ‘fit’ or convulsion
3 Looks mottled, bluish, or pale
4 Has a rash that does not fade when you press it
5 Is very lethargic or difficult to wake
6 Feels abnormally cold to touch.
A child under five may have sepsis if he or she:
1 Is not feeding
2 Is vomiting repeatedly
3 Has not passed urine for 12 hours.
(UK Sepsis Trust, 2019)
Since sepsis is life-threatening and so common, it is essential that nurses learn to recognise some of the key features of this medical emergency early in their training. To help develop your knowledge, read through Mary’s case study.
Case study: Mary – sepsis evidence-based practice
Mary is 72 and has become extremely unwell over the last 24 hours. She has become increasingly breathless and is expectorating green sputum. She was seen by her GP who sent her into her local hospital as an emergency admission. On admission, Mary was fully conscious and alert but slightly confused. Her temperature was 38°C, her heart rate was 125, her blood pressure 110/58, respiratory rate 26 breaths per minute and oxygen saturation 92 per cent on room air. Mary’s vital signs were recorded using the NEWS 2 (National Early Warning Scoring) system (Royal College of Physicians, 2017) and her total score was calculated as 11. Any score of 7 or above should trigger an emergency response by a clinical team with experience in caring for critically ill patients.
Mary was seen by the critical care outreach team and transferred to the High-Dependency Unit where the Sepsis Six Pathway (Sepsis Trust, 2019) was initiated: oxygen was administered, blood cultures were taken, intravenous antibiotics were commenced and a urinary catheter was inserted to measure Mary’s urine output accurately. Serial lactates were checked. A raised serum lactate (> 4 mmol/L) is associated with a significantly increased mortality rate. Lactate levels rise during sepsis from both aerobic and anaerobic sources as well as reduced lactate clearance. Mary gradually recovered and was able to return home two weeks after her admission.
Mary’s case study highlights that although sepsis is immediately life-threatening, if it is recognised early and treatment initiated quickly, even elderly patients can recover.
Not all bacteria are pathogenic or harmful; indeed, some are essential to human survival and health. Bacteria are found in huge numbers within and on the surface of the human body where, together with other microorganisms, they form the microbial biome. It has been estimated that there are around 23 times more bacterial cells associated with the human body than human cells, and although it has been known for a long time that certain bacteria such as those found in the colon play key roles such as synthesising vitamin K (a key clotting factor), the complex roles of the microbial biome are still poorly understood.
Cells as targets for drugs
Virtually all drugs used by nurses exert their effects at a cellular level. A good example would be synthetic insulin that is used to control the blood sugar levels of patients with diabetes mellitus. Synthetic insulin mimics the naturally produced insulin of the pancreas, stimulating human cells to take up glucose from the blood. Human cells are able to recognise each other using the glycoproteins embedded in their cell membranes; these protein markers can also allow drugs to target specific cell types within the body. To conclude this chapter, we will return to Josie who was recently diagnosed with breast cancer.
Case study: Josie revisited – breast cancer evidence-based practice
Josie was fortunate to detect the lump in her breast while the tumour mass was small and quickly underwent surgery (lumpectomy) to remove the cancerous tissue. Following histological examination it was determined that the malignant cells forming Josie’s tumour expressed the human epidermal growth factor receptor 2 (HER2). Drugs that block this receptor such as Herceptin have recently become available, which provide a new tool for treating breast cancer.
Herceptin can slow the growth of breast tumour cells and when used in early breast cancer can reduce the risk of recurrence. Josie was relieved to be told by her consultant that since her tumour mass was small, chemotherapy would not be required and since beginning
