Bronchopulmonary segments and cell cycle

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  • 1. QUESTION: DESCRIBE THE BROCHOPULMONARYSEGMENTS OF THE RIGHT AND LEFT LUNGS AND DISCUSSIT CLINICAL SIGNIFICANCE CLINICAL SIGNIFICANCEDEFINITION: a bronchopulmonary segment is the smallest 1) Surgically resectable with little or no bleedingsurgically resectable subdivision of the lobes of the lungs, depending on the lung surgeon.supplied exclusively by a tertiary (segmental) bronchus and 2) Inflation of any malignancy can be confined to athe corresponding tertiary branch of the pulmonary artery particular segment because of the intersegmental(segmental pulmonary artery) septa.CHARACTERISTICS OF EACH BRONCHOPULMONARY 3) For Radiological interpretation: once u have aSEGMENT knowledge of the BP segment 1) SHAPE: Pyramidal-shaped, with the apex facing the 4) Segmental Atelectasis whereby air is not getting lung root and their bases on the pleural surface. into a blocked BP segment. However other segments may compensate for this. 2) Separated from adjacent segments by connective tissue septa. ANATOMICAL SIGNIFICANCE: 3) Supplied independently by a segmental bronchus 5) Forensics purpose – as in determining of the cause and a segmental pulmonary artery of victim’s death is via say, atelectasis or 4) Drained by intersegmental parts of the pulmonary suffocation veins that lie in the connective tissue. 5) Named according to the segmental bronchi supplying them 6) NUMBER: 10 on the right and 8-10 on the left 7) Surgically Resectable.NAMES OF THE BRONCHOPULMONARY SEGMENTSFOR THE RIGHT LUNG: the names of the bronchopulmonarysegment include: 1) FOR THE SUPERIOR LOBE: apical, posterior and anterior (APA) BP segments 2) MIDDLE LOBE: Lateral and medial BP segments 3) INFERIOR LOBE: superior, anterior basal, posterior basal, medial basal and lateral basal BP segments.FOR THE LEFT LUNG: 1) SUPERIOR LOBE: apical, posterior, anterior, superior and inferior (APASI) BP segments. The apical and posterior segments r sometimes called apicoposterior segment. The superior and inferior segments r stms called the lingular segement. 2) INFERIOR LOBE: superior, anterior basal, posterior basal, medial basal and lateral basal BP segments. Anterior basal and medial basal r sometimes combined into anteromedial basal BP segment. 1
  • 2. QUESTION: DESCRIBE THE CELL CYCLE, USE ITS KNOWLEDGE - Cell growth also occurs here.TO CHARACTERIZE BODY CELLS - Chromosomes start to become condensed.DEFINITION OF CELL CYCLE: - Mitotic spindles begins to formIt is a series of events that take place in a cell leading to itsdivision and duplication (replication). M phaseIn prokaryotic cells, the cell cycle occurs via a process termed - Period of cell divisionbinary fission. In eukaryotes, the cell cycle can be divided in - There of 2 types of cells division: mitosis and meiosis.two periods: interphase and the mitosis (M) phase.PHASES OF CELL CYCLE IN EUKARYOTES - In both cases a cell growth stops, and the cell divides to form daughter cells with each of the replicated 1) INTERPHASE: which is divided into 3 chromosomes entering each daughter cells. a. G1 phase - Is subdivided into prophase, prometaphase, metaphase, anaphase and telophase. b. S phase – DNA synthesis phase - In mitosis these sub-phases occur once to give 2 c. G2 phase daughter cells. In meiosis these sub-phases occur twice to produce 4 daughter cells. 2) G0 phase - a SPECIAL interphase period - IMPORTANCE: 3) M PHASE (mitotic phase) o To form germ cellsG1 PHASE (gap 1 phase): o To form tissues and organs - The first phase within interphase, from the end of the previous M phase until the beginning of S phase. o To ensure continuous replacement cells with limited life-span. - Increased synthesis of new cell organelles and materials needed for DNA replication in S phase. G0 phase - Cell metabolic rate is high - A dormancy phase where the cell has left the cycle and stopped dividing. - Cells growth occurs - It is a modified G1 phase. - DURATION: highly variable, even among different cells of the same species. - It doesn’t mean that the cells are inactive; the cell r still able to carry out their main life’s functions. ForS phase e.g. a healthy liver cell is still able to break down Hb, synthesize proteins (albumin, angiotensinogen …etc), - Phase of DNA, and consequently, chromosome and so on. It does not need to synthesize proteins for replication. S phase or for M phase (meaning it does not enter G1 and G2 phase respectively) and consequently, it does - Here, xsome is not visible (because they have not enter S and M phases. stretched out/ extended). CLASSIFICATION OF CELLS BASED ON THE ACTIVITY OF THE - DURATION: very short, [because the base pairs are CELL CYCLE now exposed – due to stretching of chromosomes – and r sensitive to drugs or mutagens such as - LABILE CELLS: goes through cell cycle spending little nicotine]. or no time in the G0 phase, in order to replace lost cell or to maintain the turn-over of cells. E.g. skin cells,G2 phase: blood cells, cells in the GIT, basal cells… etc. - Gap between DNA replication (or synthesis) and mitosis (M phase). - STABLE CELLS: tend to stay in the G0 phase especially in the case where the tissue has grown to its full size. - Also there is intensive cellular synthesis particularly of If some of the cells in the tissue r removed or injured, materials (like microtubules) needed for the M phase the remaining healthy cells undergo cell division to replicate lost/injured cells. After fully replacing the 2
  • 3. damaged cells, the healthy cells go back to the G0 phase. E.g. liver cells, smooth muscle cells, skeletal muscle (limited regeneration; source of regenerating cells is believed to be satellite cells) - PERMANENT CELLS: are not capable of regeneration. As such they remain permanently in the G0 phase. If there is damage to the cell, other healthy ones cannot replace it; the damage is permanent. E.g. neurons, cardiac muscle cells (have no regenerating capacity beyond early childhood; injured cells r replaced by scar tissue).BY CHINEDU HENRY DURU (UNILORIN,NIGERIA) 3
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