# A nurse is assessing a client's gastrointestinal system. Which anatomical structure is primarily responsible for the absorption of water and electrolytes in the digestive process?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=540486  
> language: ko  
> subject: Adult Health

## 문제

A nurse is assessing a client's gastrointestinal system. Which anatomical structure is primarily responsible for the absorption of water and electrolytes in the digestive process?

## 보기

1. Large intestine (colon) **✔ 정답**
2. Small intestine
3. Stomach
4. Esophagus

**정답: 1**

## 해설

The large intestine (colon) is the primary site for water and electrolyte absorption in the digestive system, absorbing about 80-90% of remaining water from chyme.
- Option 2: Small intestine - Primarily responsible for nutrient absorption, not water and electrolytes.
- Option 3: Stomach - Involved in digestion and acid secretion, not significant water/electrolyte absorption.
- Option 4: Esophagus - Functions in swallowing, with no role in absorption.

## 심화 해설

Anatomical Focus of the Question

The question asks which structure is primarily responsible for the absorption of water and electrolytes. While multiple organs contribute to digestion, the functional distinction between the small and large intestine is a high-yield concept for the NCLEX-RN.

Physiological Rationale

The digestive tract has a clear division of labor. The small intestine is the primary site for the absorption of nutrients, including amino acids, sugars, lipids, vitamins, and minerals, through the intestinal mucosa [1][2]. In contrast, the large intestine (colon) is specifically tasked with the reabsorption of water and electrolytes [1]. This process reclaims fluid from the indigestible food residue, compacting it into formed stool for elimination [2]. The stomach is mainly involved in churning and initial protein digestion, while the esophagus serves only as a conduit for food passage.

Clinical Application

Understanding this functional specialization is critical for predicting the consequences of intestinal pathology or surgical resection. For example, a client who has undergone a colectomy (removal of the colon) will struggle with massive fluid and electrolyte loss, leading to dehydration, because the colon's reabsorptive function is lost. Conversely, extensive resection of the small intestine results in severe malabsorption of nutrients, causing malnutrition and steatorrhea, even if the colon remains intact.

Cellular Mechanism Insight

The reabsorption of water and electrolytes in the colon is not a passive process but relies on specific transport pathways. Research highlights that the colon's epithelium acts as a selective barrier, permeable to water but restrictive to harmful agents [2]. At a molecular level, key transporters facilitate this. For instance, the Na+/H+ exchanger 3 (NHE3) is a primary pathway for sodium absorption, and Cl-/HCO3- exchangers (DRA/PAT1) handle chloride absorption . Water follows the osmotic gradient created by this active electrolyte transport. Disruption of these transporters, as seen in certain types of diarrhea or in conditions like diet-induced obesity, directly impairs the colon's ability to reclaim water, leading to fluid loss .References (research sources)

- [1][Series: Important medical-dental interactions. Oral manifestations in patients with intestinal diseases].Research articleBrand HS, Boukema IC, Oldenburg L, Opperman RCM, de Boer NKH. (2026) · DOI: 10.5177/ntvt.07/08.26020

- [2]Gut mechanics.Research articlePerrin L, Vignjevic DM. (2026) · DOI: 10.1016/j.cub.2026.04.028

## 임상 시나리오

Post-Intestinal Surgery MonitoringPredicting Fluid vs. Nutrient Deficits
Following a colectomy, monitor for dehydration and electrolyte imbalances because the colon's primary function of water reabsorption is lost.

Following extensive small intestine resection, anticipate malnutrition and steatorrhea due to the loss of the primary site for nutrient absorption.

CautionA client with an ileostomy (distal small intestine) loses both nutrient-absorbing surface and the entire colon, placing them at very high risk for both malnutrition and severe fluid/electrolyte depletion.

## 핵심 개념

- **Large Intestine (Colon)** — The distal portion of the GI tract primarily responsible for reabsorbing water and electrolytes from indigestible food matter, forming stool.
- **Small Intestine** — The primary site of nutrient absorption (amino acids, sugars, lipids, vitamins) in the digestive process, consisting of the duodenum, jejunum, and ileum.
- **Colectomy** — Surgical removal of all or part of the colon, which can result in significant fluid and electrolyte loss due to the absence of the colon's reabsorptive function.

---

More free questions: [기출문제](https://mymerci.kr/)

_학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요._